2012 APRIL

•• Pistons,Pistons, RingsRings && CylinderCylinder BoresBores •• CrankshaftsCrankshafts Camshafts,Camshafts, BearingsBearings andand BoresBores •• Gaskets,Gaskets, Blocks,Blocks, HeadsHeads andand ManifoldsManifolds •• Valves,Valves, SeatsSeats andand GuidesGuides c2 elgin TG_Layout 1 4/17/12 9:17 AM Page c2

Circle 100 on Reader Service Card for more information TOOL MAINTENANCE

et’s face it, when you invest in new best interest to treat them with care. At the popular tips installed in holders and ready state-of-the-art equipment, some or very least you should put a fatigue mat in to go for the next job. Lmost of that investment is in the tool- front of the work area. Another tip to prolong the life and ing. Tooling needs proper care – especially Store your pilots away from each other improve the cutting action of your tips is if you want your new machine to perform when not in use. That’s what all the little to use a cutting fluid. Tool suppliers have according to the manufacturer’s specs. vertical holes in your tool board are for. some stuff that really works well. These newer machines don’t have a clue Don’t let them bang away at each other in Seat counter-bore cutters – that your tooling is dull, bent, nicked, a drawer. Organize them according to size; Counter-bore cutters are generally fixed in burred, or not the correct size. They do mark your tool board so you know when size and the carbide tips are either index- exactly what you direct them to do, and if one is missing. able and replaceable, or they are brazed. your tooling is not up to spec you’ll trash Always wipe the pilots down when They are available in a variety of sizes and a work piece in record time. done, which cleans the machining dust off some manufacturers offer a fully adjustable With this year’s Performance Engine Parts and prevents that dust from transferring type of counter bore cutter. and Surface Finish Guide, we aim to give into the next job. Periodically check the Again don’t let them come in contact you the information you need to do the top and bottom size to ensure they are still with each other and periodically inspect common jobs successfully – and one of the accurate. They will wear over time. them for chips or burrs. They can be keys to success is starting well. That means Replace as necessary. resharpened or rebuilt by a quality supplier. being sure your equipment, and especially Three angle cutter tips – These little Always test bore or measure them prior to tooling, is in top condition. Your tooling guys are the real worker when it comes to using them on a customer’s cylinder head often has very special cutter blades, carbide cutting the seats on multi-valve overhead to insure the counter bore size is correct. pilots, extremely sensitive leveling systems cam type cylinder heads as well as per- If you run out of room on your tool and upgraded mounting fixtures to pro- formance and diesel cylinder heads. board, a clever idea is to take a 2x4 and vide the best finish – but it takes an effort Although they are readily affordable they drill 5/16˝ holes about 1 to 2˝ apart and from you to ensure it lives up to the task. are not free. bolt that 2x4 to your workstation. Then Most feature a tool board to store and Take a magnifying glass and inspect the you can mark the board and organize prep the necessary tooling. The tool board cutting edge, look for nicks, burrs and them according to size. organizes the tooling and provides some burn marks. If you find damage, you can Boring tools – Boring tips or brazed protection for the tools when not in use, sharpen the cutting edge. It won’t reshape cutters are brittle and need periodic but the operator has a huge responsibility the degree of angle, it just sharpens the inspection as well as in house resharpen- to ensure the tooling is in tip-top condi- cutting edge. ing. Always store away from other boring tion at all times. Keep the tips in a protected environ- tools and keep them sharp to maintain fast Let’s focus on tooling made from car- ment to prevent them from banging and efficient boring cycles. bide because of its universal availability. against each other. Be sure to keep the lit- Your tools are your machine’s best Carbide tooling comes in a variety of tle plastic sleeves that your supplier always friends. Treat them like it and you’ll be able forms. You have carbide counter-bore cut- ships them in. When you acquire enough to count on them when you need to. If ters, valve guide pilots, core drills, core of them, take the time to mark the outside you don’t, that job you need to get out on reamers, ID reamers and single or multi of the box and then only store that blade Friday will be compromised due to the angle cutters. Carbide is the most afford- in that box. fact that your tooling was not up to the able material that provides long life, holds Over time you will have a complete challenge. Remember – take care of your size and can be formed into a variety of and well-organized inventory of tips. In a tools and your tools will be ready for the shapes and is readily available. perfect world you would have your most task when you need them. PPSFG Carbide Pilots – To hold centricity ADVERTISER INFORMATION Page Circle Number the tooling makers started making pilots American Cylinder Head 5, 17 105, 117 out of solid carbide. However, it needs ten- Dura-Bond 7, 16 107, 116 der loving care. Carbide by its very nature Elgin Industries 2C 100 EPWI 15, 4C 115, 126 is more brittle than high-speed steel. If you EngineQuest 8, 11 108, 111 drop a carbide pilot onto a concrete floor Hastings 9, 19 109, 119 you will have many smaller, unusable car- MAHLE Clevite 12-13, 21 113, 121 RMC 3C 125 bide pilots. Since carbide pilots can cost a SCAT 3, 20 103, 120 pretty good chunk of change, it’s in your Sunnen 23 123

www.enginebuildermag.com | ENGINE BUILDER 1 2-5 Cams-Cranks-horz_Layout 1 4/17/12 9:12 AM Page 2

HORIZONTALS: CAMS & CRANKS

ngines make horsepower with their Most stock cast crankshafts have a Heat Treatment camshafts and hold it all together tensile strength of 80,000-100,000 psi, Heat treatments in general can raise ten- Ewith the crankshaft. It takes a rela- depending on how much carbon content sile strength of an alloy steel from as low tively hot cam profile to create significant is in it. The typical cast crank made of as 55,000 psi to nearly 300,000 psi in gains in horsepower, while the crank – 1053 alloy is appropriate for builds up to some cases. As far as crankshafts are con- and subsequent components – must 450 horsepower, say most experts. cerned, 165,000 psi is about the strongest handle all the stresses of converting up The biggest difference in the various crank available from billet steel alloy. and down motion to reciprocal motion. alloy steel crank materials is the grain Crankshafts should have the ability to And when you’re talking about a per- structure, heat-treating process and the stretch and bend and then return back to formance engine, those stresses are much mixture of elements. Cranks made of their original shape without any distor- higher and consequences of a failure are 4130 or 4340 for example, have higher tion. Higher end cranks are made of much greater. Therefore, selecting the amounts of chrome and nickel, which materials that allow elongation and have right parts for your build is critical to its makes them stronger. greater fatigue strength so they can with- success. If you’re building a big horsepower stand the constant pounding forces of It’s really all about relationships. When engine you may want to consider combustion without failing. the engine is at maximum output, the upgrading to a forged or billet crank Most OE cast cranks use the induc- rods and pistons are trying to shove the made of 4340 alloy steel. The 4340 billet tion heat treating method because it crank right out the bottom of the steel crank has the highest fatigue hardens the surface for the lowest cost, engine, so strength is a prime character- strength. Some budget forged cranks are and is generally easier to incorporate in a istic of a crankshaft. Concurrently, the made of a little lower grade alloy steel production environment. It also allows camshaft, which is precisely timed in and, consequently, have a lower tensile the crankshaft to be reground without relation to the crankshaft, is spinning strength rating than 4340 but still better having to undergo any further heat treat- around at half the speed of the crank. than cast iron. ments. But high performance or racing High engine speeds can sometimes be The majority of forged and billet per- crankshafts made of forged alloy steel or too much for stock valve springs to con- formance cranks are 4340 or another billet tend to use the nitridization process trol. When this happens the valves can’t high grade alloy steel, and are made instead of induction heat treatment. shut quickly enough to keep the lifters something like a cake, to borrow a loose Nitridization is slower, as well as more on the cam. Instead of following the cam analogy. There may be a lot of chocolate costly, and it puts certain demands on the lobe profile, the lifters begin to jump off cakes that look the same but the ingredi- alloying metals in the steel in order to be the lobes. And the steeper the cam pro- ents are slightly different. Manufacturers able to create stable nitrides. The advan- file, the worse the problem becomes as tend to have their own recipes for the tage with nitriding is that it can be done engine speeds increase. material even though it is 4340 alloy. at low temperatures, it produces a very To continue that analogy, creating a hard surface and the process will leave Crankshafts crankshaft is like baking a cake. some compressive residual stress in the There are currently three types of manu- Manufacturers choose all the right ingre- surface, which is good for the fatigue facturing techniques used to make dients and then pop it in the oven to see properties of the crankshaft. crankshafts – casting, forging and billet how it turns out. Using quality ingredi- The nitridization process involves machining. The design and materials of ents and the right temperature and time injecting nitrogen into the surface of the the components that you use depend for the heat treatment makes for a very crank to a depth of about .010˝ at a con- mostly on the engine and vehicle’s tasty part. trolled heat. Air is vacuumed out and intended purpose. Cranks made of 4130 alloy have a ten- replaced with a chemical that penetrates Standard, stock cast cranks are fine for sile strength rating of 120,000 to 125,000 the surface of the part, which included mild performance applications, according psi. Cranks made of 4340 and similar cranks and cams for automotive applica- to many experts. But with the plethora of alloys may have a tensile strength of tions. One of the drawbacks of nitriding aftermarket performance parts on the 140,000 to 145,000 psi or higher, and a is that the part has to be re-treated if you market today, it doesn’t take much to fatigue strength rating up to 165,000 psi do any machine work. push past this mild horsepower threshold. depending on the heat treatment and the Some crank manufacturers use a The pounding, twisting forces created by quality of the alloy. The ingredients in the “plasma nitriding” process that vacuum those trick aftermarket heads or super- cake that boost the strength are chromi- deposits ionized nitrogen on the surface charger will wreak havoc on the cast um, nickel and molybdenum. of the crank inside a high temperature crank until it fails. oven. Others use a nitrocarburizing

2 PERFORMANCE ENGINE PARTS AND SURFACE FINISH GUIDE | April 2012 3 Scat TG_Layout 1 4/17/12 9:21 AM Page 3

Circle 103 on Reader Service Card for more information 2-5 Cams-Cranks-horz_Layout 1 4/17/12 9:12 AM Page 4

CAMS & CRANKS

process that soaks the crank in a hot “fer- can do the same thing. However, if you specs can be changed to optimize the ric nitrocarburizing” salt bath, or heats can’t run a dry sump, a crank with pro- performance. The cam causes the valves the crank to 950 degree F in an oven filed counterweights is a plus. The most to open and close, and that regulates how filled with nitrogen. aerodynamic shape is a rounded leading much air and fuel enters and exits the Nitriding causes nitrogen atoms to edge on the counterweight, with a knife- combustion chamber. penetrate the surface of the metal and edge trailing edge. Knife-edging also There are two basic types of camshafts make it harder. Nitriding typically dou- helps shed oil more quickly. used commonly in most OHV V8 per- bles the hardness of the journal surface formance street applications. Most of (from 30 to 35 Rockwell C to 60 Alignment Check your older, traditional cams are designed Rockwell C). This also increases the Experts recommend checking the main to be used with flat tappet hydraulic fatigue life of the crank up to 25% or bearing housing bores (as well as the cam lifters, while most newer cams work in more. The depth of the hard surface layer bores) carefully. If they are in close align- concert with a hydraulic roller lifter. may range from as little as a few thou- ment and the diameter is in the factory While it is commonly thought that the sandths up to .025˝ inches or more specified tolerance, it may not need to be decrease in friction is the main advantage depending on how long the crank was align honed, depending on your expect- of the roller cam, experts say the benefit left in the oven or salt bath. ed level of performance. If everything is actually that the roller design allows the checks out, the block may only need to valve to be opened and closed at a much Polishing and Coating be bored and honed – but if it’s even faster rate, resulting in more area under After a crank has been ground to size, the slightly in doubt, err on the side of pre- the curve with shorter seat timing. journals are often micropolished to cision. Cam experts say it is very important improve the surface finish. Some crank For high horsepower applications, you to understand how the cams are rated suppliers have said the ideal surface finish must be more particular about toler- prior to comparing a stock cam to an for rod and main journals should be 5 ances. The main bearing housing bores aftermarket cam, and before selecting a microinches or less. are machined with a boring tool from cam. The very beginning and end of the Some crank suppliers also polish the the factory. This leaves a moderately lift curve on a stock cam is usually such entire crankshaft. This process will not rough finish for the bearing to rest that the valve opens slowly and sits down only make for an attractive finish, it also against, so the actual contact area is very gently on the seat. This setup is helps reduce the risk of surface cracks reduced to where the bearing contacts mostly used by the OEs to reduce noise forming from stress risers left over from the high spots on the surface of the bear- and seat recession, as well as improve the manufacturing process. A polished ing seat. For any high horsepower appli- overall durability. It is the area in which surface also helps shed oil at low rpm, cation, the block should be align honed. the performance aftermarket cam makers reducing windage and drag. Oil shedding This ensures that the bores will be in per- exploit in order to increase performance coatings may also be used for the same fect alignment and also provides a very and give you that mean sound most of purpose. But one crank supplier said, at flat, smooth bearing seat. your customers want. high rpm there won’t be any oil on the Even with similar lift as a stock cam, crank anyway because it will be flung off Camshafts many performance cams can have con- in operation. The development of new camshaft pro- siderably more area under the curve with But there are still power gains to be files is an ongoing process that will never quite a decrease in seat duration. To pro- found from polishing, according to some stagnate. There are a lot of proven grinds vide a better comparison of duration and experts. One company that applies a that work well in various engines and engine power, the aftermarket industry unique finishing process to their cranks combinations. Many of these grinds have has settled on .050˝ duration as a stan- that leaves a bright, chrome-like finish been popular for years. dard. While the seat timing tends to have says the reduction in friction and oil But with so many stroker engines greater influence on characteristics such retention is good for 1 to 3% more being built these days, and a proliferation as idle stability and vacuum, the .050˝ horsepower in a SB Chevy with no other of high-flow aftermarket cylinder heads duration provides the clearest indication changes, and up to a 4% increase in for a growing number of older engines, of where the engine will produce peak horsepower on a BB Chevy. cam grinders are always looking for the torque and power. next innovation that can give their cus- This holds true even when the ramp Less Drag tomers a performance edge over what’s designs are far different, resulting in sub- High revving racing cranks typically have currently available from their competi- stantial differences in seat timing. This counterweights that are shaped to cut tors. makes it possible for engine builders to wind resistance and drag as the crank The camshaft is the main component compare the .050˝ durations when spins in the crankcase. Drag slows the that will help enhance the performance selecting a camshaft’s size, and use the crank at high speed and robs power that characteristics of an engine, but it is advertised seat durations for approximat- could otherwise be put to the ground important to understand what role the ing how quickly the profile gets the though the drivetrain. A vacuum sump cam plays in the engine and how the cam valves on and off the seat.

4 PERFORMANCE ENGINE PARTS AND SURFACE FINISH GUIDE | April 2012 2-5 Cams-Cranks-horz_Layout 1 4/17/12 9:12 AM Page 5

CAMS & CRANKS

Getting the valve off and on the seat Another decision that has to be made model OHC engines don’t have cam more quickly sets the stage for either less is how much lift do you want from the bearing inserts. If the engine was over- seat timing and more area, or the more cam and rockers? For any given lift, you heated, cam bore damage is very com- common goal of similar seat timing and can use various combinations of cam lift mon. Usually the middle bores are the much more area. and rocker arm ratio to achieve the same most damaged because the head bows up As with any valve train, experts say numbers. According to one cam supplier in the middle. There are a number of there are limits on the maximum veloci- we interviewed, the best approach is to ways to salvage a damaged head. One is ty of the valve, either due to the tappet get more lift with the rocker arms and to line bore or hone the OHC cam bores design or how much velocity (and ener- less with the cam. Why? Because higher to accept a new cam with oversized jour- gy) the valve spring can control. In either lift cams are more highly loaded cams nals, or to removed the cam journal caps case, getting the valve off the seat quick- that experience more wear. and grind down the face of the caps and ly allows the valve to reach maximum Consequently, you are more apt to machine them back to standard size. If velocity sooner, gives it more time to round off a lobe on a high lift cam that there are no caps, the cam bores can be turn around, and results in increased area. has big lobes than one which uses small- enlarged to accept bearing inserts, if they It is somewhat analogous to the effect of er lobes with higher ratio rocker arms. are available for the application. 0 to 60 mph time on quarter-mile time. The valvetrain also tends to be more sta- Another problem to watch out for is a If a Top Fuel dragster took 6 seconds to ble when a higher percentage of the bent cam. It only takes a few thousandths get from 0 to 60 mph, like a respectable valve lift is generated by the rocker arms of an inch of misalignment for the cam passenger car, it would be impossible for rather than the cam lobes, lifters and to bind in the head. To check cam it to run a 4.5-second quarter-mile time. pushrods. straightness, place the cam in a pair of V- Similarly, the cam profile design cannot blocks (one at each end), then rotate the take all day to get off the seat and still OHC Cam Bores cam with a dial indicator placed on the expect to have enough area under the In an overhead cam application, line bor- middle journal. If runout exceeds specs, curve to allow the airflow needed to ing and an oversize cam may be neces- the cam is bent and needs to be straight- optimized high rpm power. sary to restore the cam bores. Most late- ened or replaced. PPSFG The biggest mistake most engine builders make when selecting a cam is over-camming the engine with too much lift and/or duration. Big numbers look impressive, and you may have a cus- tomer who insists having the wildest cam he can find for his engine, but is it the best cam for the application? The best all-around cam for a street performance engines would be one that has its peak power and torque curve in the 1,500 to 3,000 rpm range. Most domestic iron V8 street engines don’t get revved over 5,000 rpms. But if you are building a race motor you might want a cam that produces peak power and torque in the rpm range where the car will be running most of the time. Most stock and lightly modified heads won’t flow any more air once valve lift reaches about 0.550˝. Pushing the valves open any further won’t pro- duce any more power, and may actually lose some off the top end because of reversionary air flow. On the other hand, if you’re building a big race motor with highly modified heads and huge ports that can handle gobs of air, increasing valve lift to the physical limits of the engine will be necessary to make the most power possible.

Circle 105 for more information www.enginebuildermag.com | ENGINE BUILDER 5 6-9 Valve Seats_Layout 1 4/17/12 9:13 AM Page 6

VALVE, SEATS & GUIDES

n stock production engines, the Most of the street performance heads exhaust valve is designed to endure use the same size valves as OEM heads, Ithe rigors of daily commuting for While most racing and performance but many racing heads do not. The head 150,000 miles or more. But try going engines use a stainless valve of some sort, may require a valve that is slightly longer more than a few hundred miles with a that all changes when you get into high than a standard valve, or one with a dif- racing engine and you’re pushing your end pro racing. At the top levels of the ferent head or stem diameter. As a result, luck. Depending on whether or not sport, experts say titanium or Inconel valve suppliers now have to carry a your racing engine has been over- materials are preferred for their light greater variety of valve head and stem revved, the valves may last only a few weight and durability, and where cost is diameters, and lengths, or custom make races. not an issue. the valves as needed. Some valve suppli- In a NASCAR engine where most When should you upgrade valve ers say they can turn around a custom teams are now running titanium valves, materials? Engine builders are usually order in a week thanks to CNC tooling they might be replaced every race. In Pro encouraged to look at upgrading mate- that allows blanks to be easily machined Stock or Top Fuel drag racing, valves rials when they use more aggressive cam to specifications. might be replaced every half dozen runs. profiles or if the rpm band of the engine While a street/strip engine may last is increased. From a seat and guide stand- Sodium-Filled Valves more than a season, it all depends on the point, you should look for something Sodium-filled hollow stem valves are conditions under which the engines that will withstand the higher rpms and available for higher heat applications, and operate. loading of the guide from side load from are typically used for the exhaust valves. One supplier of valve train compo- a high lift cam and seats for the combi- The sodium inside the valve stem melts nents says that with the exception of nation of rpm and spring pressure. and absorbs heat from the valve heat. As Inconel big block Chevy marine and Titanium or hollow-stem valves are the valve opens and closes, the sodium supercharged valves, their performance always a consideration when trying to sloshes up and down inside the valve to valves are typically made from 21-4N lighten up the valve train. transfer heat from the valve head to the stainless material. The explanation is that stem. This helps the head run cooler to there are many grades of stainless steel, Titanium reduce the risk of valve burning, preig- and just having a valve made of “stain- Titanium valves are the lightest valves nition and detonation. less” doesn’t mean a lot. However, indus- available, weighing about 40 percent less The difference in cooling is signifi- try experts we have consulted note that than stainless steel valves of the same size cant. With a conventional solid stem 21-4N stainless steel is generally accept- with solid stems. Titanium valves are exhaust valve, 75 percent of the cooling ed as a quality material for performance mostly used in high revving engines takes place across the valve seat and 25 valves. with more aggressive cam profiles that percent through the stem. In a sodium- There are many minor variations on open and close the valves more quickly. filled exhaust valve, 40 percent of the the typical performance valve made of But titanium valves are not for every- cooling is through the stem so the valve 21-4N, and there are at least a half a body because they are more expensive can tolerate more heat. dozen different alloy variations of this than stainless. metal. The manufacturer may find that Many titanium valves are custom Hollow Stem Valves they can do something a little less machined rather than produced to stock One way valve suppliers are taking addi- expensive or make the valve last a little dimensions for specific heads: the head tional weight out of intake (and exhaust) longer by putting a hardening agent in it diameter, stem length and diameter, and valves today is offering “hollow stem” or some other treatment. The intake tip are all machined to whatever specifi- valves. The valve stem is gun-drilled and valves are all basically made from one cations you choose. This allows you to micropolished to make it hollow like a type of material and exhaust valves are get exactly what you want, and elimi- pushrod. The drilling is only done in the made from another. But some manufac- nates the need for suppliers to produce upper 2/3 of the stem where rigidity is turers will make all the valves from a 21- and stock inventory for applications that less of a factor than the area just above 4N derivative regardless of which valve may not be popular items. the valve head. After the stem has been it is. The reason for this, according to our drilled out, a hardened tip is welded expert, is because they end up buying in Valve Blanks onto the top of the stem. The result is a more bulk and therefore a more signifi- With the proliferation of aftermarket valve that is typically 20 to 22 percent cant discount than if the manufacturer cylinder heads that require unique valve lighter than a valve with a solid stem. bought half of one and half of another sizes, it has become difficult for some According to one supplier of hollow type of material. suppliers to keep up in recent years. stem performance valves, the valves are

6 PERFORMANCE ENGINE PARTS AND SURFACE FINISH GUIDE | April 2012 7 durabond TG_Layout 1 4/17/12 9:21 AM Page 7

Circle 107 on Reader Service Card for more information 6-9 Valve Seats_Layout 1 4/17/12 9:13 AM Page 8

VALVE, SEATS & GUIDES

good for 300 to 350 more rpm with no of the heat is conducted out through other modifications (same springs, rock- the valve guide. If the clearance goes up ers, pushrods, etc.). by much, the conductivity from the stem to the guide will drop like a rock Coatings – transferring it all to the guide. And During discussions with suppliers, we that’s why it’s better to use bronze have been told that coatings are being guides because they conduct heat away used in more and more applications more effectively from the water jacket these days. When it comes to valves, a even if it goes through cast iron first. number of coatings may be employed, Since the surface area of the guide is including special coatings for titanium about 4 times that of the valve stem, valves. conducting heat into 4 times the area In some cases, a metal treatment, of cast iron will cut that temperature rather than a coating, is used with pre- dramatically. mium valves. In the case of one suppli- er, treated valves go through a five step Valve Seats liquid nitriding process which intro- Hard working diesel engines, perform- duces nitrogen into the surface of the ance engines and engines that run on valve, resulting in a thin, high hardness dry fuels such as propane or natural gas case that is both wear- and corrosion- produce a lot of heat in the combustion resistant. The valve’s dimensions are not chamber and often require valve seats changed by the treatment. In addition, that are harder and more heat-resistant. the lower coefficient of friction from Stellite, chromium, cobalt, tungsten and this coating leads to better sliding, less nickel alloy valve seats are commonly risk of scuffing at the guides and used for such high heat applications as improved durability against wear on are tool-steel valve seats. Beryllium- both the guide and the stem. copper or copper-nickel alloy seats are often used in racing applications, typi- Valve Guides cally with lightweight titanium valves. Bronze valve guides are most widely Average combustion temperatures used in European and racing applica- in a street performance engine can tions. Powdered metal (PM) guides are range from 1,400 to 1,700 degrees F. mostly used in stock automotive Nickel alloy cast seats can usually han- engines as well as cast iron guides. dle 1,400 degrees F with no problem, Diesel engines often use coatings on while cobalt is good for up to 1,650 to cast iron guides to combat the wear in 1,700 degrees F. With nitrous oxide, newer, low sulfur diesel applications. temperatures can soar to 4,400 degrees One race engine expert pointed out F, which can make some seats become some interesting observations he has hard and brittle. This increases the risk made over the years. He believes worn of seat cracking and failure. valve guides cost more horsepower on Every valve seat supplier makes a big the dyno than you might think. In one deal about the advantages of their pro- experiment with a test engine, he went prietary alloys – and rightly so. The from .002˝ to .004˝ to .006˝ on intake strength, hardness, wear resistance and valve clearance. The results revealed thermal properties of a valve seat alloy that the engine had dropped four can make or break it depending on the horsepower from .002˝ to .004˝. He application. lost one horsepower per cylinder on a An alloy that lacks the hardness and 4-cylinder test mule, and from .004˝ to wear resistance for a high-heat, high- .006˝ he lost another nine horsepower. load engine application won’t hold up According to this expert, that’s not very well. As a general rule, the higher going to be the case for every single the operating temperature of the engine out there, but the test mule engine and the higher heat loads it responded very similarly to a small must endure, the higher the grade of block Chevy. seat alloy that will be required to han- Additionally, he says that 40 percent dle the job. Cut corners here with a set

Circle 108 for more information 8 PERFORMANCE ENGINE PARTS AND SURFACE FINISH GUIDE | April 2012 6-9 Valve Seats_Layout 1 4/17/12 9:13 AM Page 9

VALVE, SEATS & GUIDES

of cheap replacement seats and you’ll is in good condition will ensure you can ance engine builders say they see the probably regret it later. hold tight tolerances. Being off due to best flow numbers using a 58° undercut Titanium valves do not cool as well poor equipment won’t do your valve below the primary seat, and a 70° cut as stainless steel valves, so they require job or reputation any good. The pilot- below that. Using a steeper top angle of valve seats that conduct heat at a much to-guide clearance should be .0002˝ or 33° to 37° on the intake seats also helps higher rate. For many years, the seat less for accurate machining. One way to reduce turbulence as the air enters the alloy of choice for titanium valves was achieve that is to use a high pressure combustion chamber. Others use special beryllium copper, which conducts heat lubricant on the pilot. cutters with an infinite radius or a three to as much as six times faster than The seat cutter must be sharp and CNC-controlled single point cutter to most iron alloys. spun at a high enough speed to produce contour the seat above and below the Beryllium copper valve seat alloys a high quality finish on the seat. Any primary 45° seat to optimize flow. typically contain only about 1.5 to 2.5 chatter while cutting a seat may be from Unfortunately, there’s no tried-and- percent beryllium. But that’s enough to too much play between the pilot and true formula that works best for every create a seat material that provides high valve guide, slow cutter speed, or the engine. It takes a lot of time on a dry or thermal conductivity along with the machine isn’t level. Using a coolant wet flow bench to figure out which durability required for titanium valves in when cutting hard seats will also reduce angles are going to produce the best a high performance engine. chatter. results. And sometimes what looks good Some Be-Cu valve seats are 97% The commonly used 30-45-60 on a flow bench doesn’t always produce copper with 1.8 to 2.0% beryllium, and degree three-angle performance cut will more power because of fuel separation have a hardness of 38 to 41 Rockwell flow better than a seat with a single 45 problems at the valve and seat interface. C. Other alloys contain less beryllium degree cut. But more angles breathe Because of this, experts say it often takes (0.2 to 0.6%) but add nickel (1.4 to even better. Adding additional cuts some trial-and-error experimentation to 2.2%) to reduce hardness to 20 under the seat, and using steeper angles find the optimum combination of angles Rockwell C. By comparison, ductile generally helps the airflow numbers or seat profile that delivers the most iron seats typically have a hardness of even more. Some well-known perform- power and throttle response. PPSFG around 32 Rockwell C. But beryllium copper seats have some drawbacks. One is that the alloys are expensive. Another is that beryllium is a toxic metal. There’s no risk in han- dling the seats, but any dust that’s creat- ed with machining the seats can be haz- ardous. In recent years, proprietary copper- nickel alloy valve seats have replaced Be- Cu seats in many performance and high heat applications. Some of these new copper-nickel alloys have a thermal conductivity rating of up to 90 BTU per foot per hour per degrees F, which is more than enough to provide adequate cooling for titanium valves or stainless steel valves in high output or high heat engines.

Seat Installation, Finish Tips On a high performance engine, a multi- angle valve job is an absolute must to optimize the breathing potential of the cylinder head. But first you must install or recondi- tion the valve guides before you do any seat work. The center line of the valve guide will determine the location and concentricity of the valve seat. Using a valve-and-seat machine that

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CYLINDER HEADS & MANIFOLDS

he top end of the engine is all about that are designed to deliver high rpm numbers at peak valve lift may be impres- moving air and fuel to the combus- power for racing applications instead of sive, but what’s usually more important is Ttion chamber as efficiently as possible building the engine to produce more low- how well the head flows at partial valve lift and to produce as much power as possible end and mid-range torque. Even in all-out as the valves are opening and closing. in performance applications. Today’s after- racing the engine with the biggest heads Better flow characteristics at partial valve market cylinder heads and intake mani- and biggest flow numbers doesn’t always lift can have more of an effect on power folds offer engine builders a lot of win the race. and torque than big airflow numbers at options – but choosing the right compo- Experts say cylinder head performance peak lift. nents for your build is more than just find- is not just about huge flow numbers and Accurate cylinder head comparisons ing the biggest flow numbers. port volumes, it is the proper sizing and mean you should look at the entire flow Experts say it is important to match the velocity that determines how well a cylin- curve from low lift to maximum lift. Once head and intake to your application and der head performs. As time has gone on, you’ve done that, you will have a much intended use, specifically relating to rpm the lines between street and race have better picture of how the head will actual- range. If your customer is an occasional become so blurred that it depends on ly perform on the motor you are building. drag strip competitor but mostly drives his whom you talk to whether an engine or Also, there’s more to airflow than big showpiece to the local diner for car club component is for race or street. cfm numbers. Air velocity and swirl are nights, you may want to choose some- The best way to compare cylinder also important. A port that’s sized proper- thing that will be more streetable but still heads is to bolt them on an engine and do ly for the engine displacement and rpm have reasonable performance from stop- a series of dyno test runs to see how they range will keep the air moving at higher light to stoplight. Of course, today’s per- perform. The best head is not necessarily velocity, resulting in more complete cylin- formance components blur the lines the one that makes the most peak horse- der filling and more power. Air velocity between street and racing more than ever, power in a narrow rpm range, but the one affects both throttle response and low-end so you must know how to read between that delivers the best power and torque torque. That’s why heads with port runner the lines for your customers. curves for the intended application. If volumes that are too large for a given you’re building a motor for a drag car, engine application may not perform as Cylinder Heads then peak high rpm power is what you well as a stock cylinder head. There are a lot of people who believe in want. If the engine is going into a circle Swirl helps route air into the cylinder the “bigger is better” philosophy when it track car, you want good throttle response more efficiently and promotes better air comes to selecting cylinder heads. and peak power in the mid to high rpm and fuel mixing for better combustion. Aftermarket cylinder head manufacturers range. For a street application, a broad, flat Swirl and turbulence can also cause air and head porting specialists like to brag torque curve and lots of low- and mid- and fuel separation in the combustion about the latest cubic feet per minute range torque works best. chamber, which is something that can be (cfm) flow numbers they’re able to achieve Airflow depends on valve lift, valve visualized by wet flow testing. using the magic of flow bench testing and area, air density and the test pressure. There Valve angle (the angle of the valve stem CNC machining. But even with the big are industry-standard methods for cali- with respect to the deck surface) also flow numbers, the numbers can some- brating flow benches and correcting air- affects airflow, and here shallower is usual- times be misleading because of the way flow numbers to compensate for differ- ly better. The configuration of the com- they are measured. ences in air density. But airflow values can bustion chamber, valve shrouding and Heads do make horsepower, but they vary somewhat from one flow bench to even the diameter of the cylinder bore are don’t make it all by themselves. A set of another, depending on the methodology additional factors that also affect airflow killer aftermarket performance heads that and equipment that is used. Most flow and a head’s ability to make power. is mismatched with a camshaft, valve train benches have a margin of error of around or induction system will never realize the plus or minus one percent. On a cylinder What’s Hot engine’s full potential. It’s all about achiev- head that flows 400 cfm, the margin of The 600 cubic inch “monster motors” of ing optimum airflow and velocity within error could be plus or minus 4 cfm either a few years ago seem somewhat insignifi- the rpm range where the engine is built to way. cant compared to the 850 and 900 cubic produce power. Another point to keep in mind when inch motors that are now commonplace That’s where many street performance comparing airflow numbers is that the in the market. There’s even a 1,000 cubic engine builders have gone astray. They valves reach maximum lift only once dur- inch naturally aspirated engine that makes overbuild the engine with components ing the intake and exhaust strokes. Flow over 2,150 horsepower and 1,550 lbs. of

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Circle 111 on Reader Service Card for more information 12-13 Mahle spd TG_Layout 1 4/17/12 9:20 AM Page 12 Circle 113 on Reader Service Card for more information 12-13 Mahle spd TG_Layout 1 4/17/12 9:20 AM Page 13 Page AM 9:20 4/17/12 1 TG_Layout spd Mahle 12-13 10-16 Decks-Gaskets2_Layout 1 4/17/12 9:15 AM Page 14

HEADS & MANIFOLDS

torque. It’s hard to tell how far this trend performance cylinder heads is CNC pro- depends on what you are trying to will push engine displacements in the file heads. These heads are developed, typ- achieve. years ahead. ically by hand, through porting, grinding Is the end result better than the best “as The bigger these engines get, the more and then testing them out to see how they cast” head for a given engine application? air the cylinder heads have to flow to han- perform. Once a head is shaped by hand it It depends on the castings that are avail- dle the added cubic inches. The availabili- is mapped by computer for its characteris- able and how well they flow compared to ty of aftermarket engine blocks with tics and port configurations of that appli- an optimized CNC port configuration for wider bore spacing continues to expand, cation. People who do this kind of work the same setup. With most high-end per- and with it the availability of larger cylin- build up a digital library of port configu- formance heads, a raw casting is CNC der heads to fit these engines. rations that work well with various head machined to specific dimensions for that Another trend that is more prevalent in castings, camshaft and engine combina- application to deliver peak performance. today’s cylinder heads is reduced valve tions. This allows them to replicate a stem angles and raised ports for increased proven port configuration by entering the Manifolds airflow. This often requires custom fabri- data into a CNC machine and removing A well-designed manifold that is properly cated intake manifolds or special intake the unwanted metal to modify the cylin- matched to the engine’s requirements will manifold castings to mate with the modi- der head. make more torque and horsepower than a fied heads. With these types of heads, There is some debate as to whether or manifold that is mismatched to the installation is not a simple swap. Changing not ports in an “as cast” cylinder head flow engine. An intake manifold is more than the head may also require changing the as well as those in a CNC machined head. the plumbing that connects the carburetor intake and exhaust manifolds, and possibly Many aftermarket performance cylinder or throttle body to the ports in the cylin- even the valve train configuration. heads that are sold with “as cast” ports are der head. It is an integral part of the For small block Chevy applications, capable of delivering excellent perform- induction system that has to match the splayed valve symmetrical heads are avail- ance out of the box with no additional airflow characteristics of the cylinder head able to replace siamese-style SBC heads. modifications. The same goes for some and camshaft, as well as the displacement The symmetrical heads seal better and stock heads (such as Chevy LS1 heads) and rpm range of the engine. reduce the risk of head gasket failure in that flow very well in their stock configu- The sole purpose of your intake man- the hot spot area between adjacent ration. But there’s always room for ifold is to provide the best possible pas- exhaust valves on siamese style heads. The improvement by either hand porting or sageway for air and fuel from your carbu- ports also provide a straighter shot at the CNC machining “as cast” heads to change retor to your cylinder heads. Performance valves than the ports on siamese heads. the contours of their ports, bowls and intake manifold manufacturers offer sever- Another feature that is abundant in combustion chambers for better flow. It al different options to get air and fuel from carb to heads.

Intake Styles Carbureted intake manifolds come in a variety of styles: dual-plane, single-plane, air-gap, tunnel ram and others. Choosing the right design comes down to matching the intake style to your customer’s vehicle and intended rpm operating range. Dual-plane intake manifolds, also sometimes called 180-degree intake man- ifolds, have two separate plenums that accept air/fuel from the carburetor. Each one of the plenums, or openings, feed four cylinders on a V8 engine. This divided design ensures that each bank of four cylinders only sees every other firing pulse (or 180 degrees of crank rotation), so there’s less overlap between induction pulses. The result is a cleaner induction pulse, particularly at low rpm. Dual-plane intake manifolds also typically have longer Cylinder head performance is not just about huge flow numbers and port intake runners, making them ideal for low volumes, it is the proper sizing and velocity that determines how well a cylinder and midrange power production. head performs. Choose a dual-plane manifold for:

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HEADS & MANIFOLDS

• Low-rpm response, power in the need to choose a manifold that fits your intake ports on your cylinder heads. 1,500-6,500 rpm range engine. Whether you’re shopping for a On the top end, you need to make sure • Good idle quality carbureted or fuel-injection intake mani- your new intake manifold will work with • Street performance, mild racing fold, consider the following factors: the carburetor’s mounting pad configura- Single-plane intake manifolds use a • Hood clearance tion. Four-barrel carbs, for example, are single open plenum, which feeds all eight • Cylinder head port design available with three basic mounting pads: cylinders on a V8 engine. Although this • Carburetor/throttle body mounting square bore, spread bore, and Dominator design doesn’t provide the dual-plane’s For street applications, hood clearance style. Check to see what type of mounting clean induction pulse in the low-rpm is a major consideration. If your customer pad your carburetor uses and then make range, it generally allows for better, more wants to retain the use of his hood, meas- sure the intake matches up with it. If equal flow distribution between cylinders. ure the height of the stock manifold and you’re buying a fuel-injected manifold, In addition, single-plane intakes typically try to remain close to that dimension make sure the throttle body inlet works have shorter, more-direct runners, so when choosing a performance intake with the throttle body size. they’re able to move higher amounts of air manifold. Your customer can accommo- from the carb to the heads. date higher intake manifolds by using a Fine Tune Choose a single-plane intake mani- hood scoop, low-profile air cleaner assem- Once you and your customer have settled fold for: bly, or other means. But remember, this on a general intake style, confirmed the • High-rpm horsepower through will result in added time and cost. proper port style, and verified the carb 8,000 rpm Cylinder head port design is also an mounting pattern, you may decide to look • Racing applications important consideration. For example, big at all the little details that separate each While dual-plane and single-plane block Chevy heads are available with mul- intake manifold. If you live in an area that intake manifolds are the most common tiple ports designs, including rectangular, employs special emissions regulations (i.e., intake styles, there are a few additional oval, and peanut-style. Always make sure California), look for a CARB E.O.-certi- options available. “Air-Gap”-style intake the intake runner ports match up with the fied intake manifold. You can also compare manifolds, reportedly improve on the typ- ical dual-plane design by raising the intake runners. By adding extra space between the bottom of the intake and the engine, the runners are kept cooler and the intake charge remains colder and denser. Choose an Air-Gap-style intake for: • More power from idle-5,500 rpm • Street performance Tunnel ram intakes are dual-carb intakes that became popular on dragstrips in the 1960s and ’70s. These distinctively tall single-plane intakes utilize longer run- ners than typical single-plane manifolds, effectively expanding the rpm powerband. Keep in mind, the dual-carb design calls for additional tuning, and the dimensions of the intake require more space. Choose a tunnel ram intake for: • High-rpm power • Racing and wild street applications • Aggressive look Depending on your application, you can also find a wide range of dual-quad and tri-power intake manifolds for multi- carb setups. Like single-carb manifolds, these intakes are available in dual-plane, single-plane and even Air-Gap designs.

The Right Fit Once you’ve selected the right intake manifold style for your application, you

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HEADS & MANIFOLDS

port cross-section, plenum volume, and metal as it sweeps across the surface. If specific runner lengths to really narrow you’re wet grinding a block, the pressure down your choice. and cutting action of the stones can change as the grinding head rides over Machining and Sealing the surface. The metal between the cylin- Sealing problems are inherent in bi-metal- der bores creates more resistance and cuts lic engines because aluminum cylinder differently than the areas around the heads heat up much faster than cast-iron cylinder bores. This may leave a lot of cylinder blocks during the warm-up waviness across the surface of the block. cycle. The metallurgical differences mean You won’t get that with dry milling. It the aluminum cylinder head tends to will cut the block flat with no high spots. expand at a much faster than the cylinder Experts contend that the type of block does throughout the entire engine process or equipment used to surface a cycle. This difference in expansion rates head or block doesn’t usually matter as between aluminum and cast iron creates a long as it leaves a good finish. Engine scrubbing effect that eventually wears out builders can dry mill or wet grind or the stainless steel “fire ring” that keeps sand and get good results when the combustion gases from entering the cool- resurfacing is done right. However, for ing system. performance applications, smoother is Because the cumulative effect of these better. repeated thermal events results in failed Industry spokespeople say increasing- cylinder head gaskets, most aftermarket ly often there’s a growing need to de- gasket manufacturers have designed head emphasize Ra numbers and focus more gaskets using space-age materials that on Rz when discussing surface finish. resist scuffing wear in bi-metallic applica- Roughness Average (Ra) can actually tions. have a wide variance across a given sur- Head gaskets require a surface that is face profile. Rz, which is the average dif- smooth and flat to cold seal and hold a ference between the peak height and val- lasting seal. ley depth, is a more accurate representa- When multi-layer steel (MLS) head tion of true surface topography. gaskets became commonplace a number While still important, today’s surface of years ago, there was a lot of concern finish requirements are not are critical as that aftermarket surfacing procedures they were even recently, say experts. In might not be able to reproduce the mir- the past, manufacturers recommended an ror-like finish that the vehicle manufac- 8 to 10 Ra finish to seal the head gasket. turers said was absolutely necessary to But according to one prominent gasket seal MLS head gaskets. The challenge was manufacturer, the coatings on today’s to duplicate the factory finish using out- aftermarket MLS gaskets can handle any- dated equipment and methods that may thing in the 40 to 70 Ra range with no or may not produce the desired results. problems. Aftermarket equipment suppliers rose Smoother is better for many applica- to the occasion and introduced a new tions, but is not absolutely necessary, generation of high speed precision depending on application. For example, if milling machines that could meet or you’re building a high-end race engine exceed the factory surface finish require- that tends to run hotter, a surface finish ments for original equipment MLS head of 30 Ra or less is better and recom- gaskets. Wet grinding was out and dry mended. But for a typical street or strip milling was in as the new way to surface application, it is acceptable to use an cylinder blocks and heads. Wet grinding MLS gasket with a coating that is more was capable of producing high quality conformable to handle a more tradition- surface finishes when done properly. But al surface finish. it has been called, somewhat conserva- Some coated MLS gaskets can handle tively, perhaps, a “very messy” process surface finishes from 70 to 80 Ra. More compared to dry milling. conventional coatings that are designed Grinding requires pressure to cut for surface finishes of 30 Ra or less are metal. Dry milling does not, it shaves also available in the aftermarket. PPSFG

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Circle 117 on Reader Service Card for more information 18-22 Piston Rings-Cylinder Bore_Layout 1 4/17/12 9:15 AM Page 18

VERTICALS: PISTONS, RINGS & BORES

ood bore geometry improves ring longer than vitrified abrasives, but they are sealing to maximize power while also quite a bit more expensive. But a set of Gminimizing blowby, compression provided by this type of ring. diamond stones can typically hone up to losses, emissions and oil consumption. You can check bore geometry with a 10,000 holes before they wear out. Most engine builders know that if you gauge to measure the inside diameter of A honing machine that offers variable don’t bore and hone the block with a the cylinder, but that won’t let you see speed stroking and can dwell in the bore torque plate that creates a simulated load, what the bore actually looks like in three while maintaining the same load reading the hole won’t stay perfectly round. As dimensions. A bore that appears to be will produce better bore geometry than a soon as the head is installed and bolted round may actually have some taper, dis- machine that lacks these features. Using a down, the head bolts will pull the bore out tortion or misalignment in various areas as coolant that is compatible with your hon- of round, which could affect the sealing you go from the top of the bore to the ing stones will also improve bore geome- ability of the rings between the bore wall. bottom. Most shops don’t have the equip- try. The coolant flushes away debris while And this is especially true in performance ment to do three dimensional mapping – helping the stones maintain a consistent engines that are eking out every bit of all you can do is make sure you are using temperature. You can use synthetic water power through thin, low tension rings. proper honing and finishing procedures so based coolants or honing oil with dia- The main function of the cylinder bore hopefully the bore will be round and mond, but honing oil only with vitrified is to provide a wear-resistant bearing sur- straight. abrasives. face to support the piston and rings, and Diamond honing stones typically deliv- retain enough oil to keep the rings lubri- er the best bore geometry because dia- Tips cated. When boring and honing cylinders, mond is more consistent than vitrified For performance engines, experts recom- the following criteria are absolutely critical honing abrasives – especially with less mend surface finishes that are a bit in order to achieve the best results: experienced honing machine operators. smoother than stock, but regardless of the • Bore geometry and straightness. This Consequently, there’s less risk of machin- specification, the best rings seal is achieved is necessary for good ring seating and seal- ing taper into a cylinder bore when hon- by plateau finishing the cylinders. ing, the straightness of the sides of the bore ing with diamonds because there is almost There are as many recipes for plateau (to minimize ring flex as the piston moves no wear on the stone. Diamond honing finishing as there are for making pizza. The up and down), and its alignment to the stones are easier, faster and last much objective is to create sufficient crosshatch bore center and crankshaft. The bore depth in the cylinder wall to retain must also be accurate dimensionally so oil with a relatively flat, smooth flat the piston will fit with proper side surface area between the grooves clearances. to support the rings. A plateau fin- • Surface finish. The average ish will essentially mimic a broken- roughness, peak height and valley in cylinder. This will drastically depth of the surface must be compat- reduce the time it takes for new ible with the type of rings that are rings to seat, and also minimize used. ring wear during the break-in • Crosshatch angle. Should be process for longer overall ring life. within a specified range for the appli- Rings manufacturers say the cation to provide proper lubrication best surface finish is often achieved and oil control. by rough boring a cylinder to Too much cylinder bore taper can within .005˝ of final dimensions cause the rings to flex in and out as (or rough honing to within .003˝ the piston slides up and down, which of final size), then honing with is not good. Excessive taper can lead #220 grit stones down to the last to ring breakage as well as interfer- .001˝, and finishing with a #280 to ence problems if the ring end gap #400 grit stone (depending on the butts together or is not able to handle application). Brushing the cylinder the change in bore diameter. With with a plateau honing tool as the gapless rings, good bore geometry final step removes loose and folded and taper are even more important to Using a coolant that is compatible with your honing stones will surface debris, and does not alter minimize blowby and compression also improve bore geometry. The coolant flushes away debris the dimensions of the bore. losses and to maximize the benefits while helping the stones maintain a consistent temperature. Accurately measuring the sur-

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PISTONS, RINGS & BORES

face finish in a freshly honed cylinder for good oil retention and lubrication. • Rk = 25 to 30 requires an instrument called a profilome- Some performance engine builders run • Rvk = 35 to 40 ter. The profilometer drags a diamond- somewhat higher Rvk (valley depth) The same rough honing procedure as tipped stylus across the surface to calculate numbers in the crosshatch to improve oil before would be used, but the second step a number of important parameters includ- retention in high revving engines. would be six strokes with #550 grit dia- ing: roughness average (Ra), peak height According to one ring manufacturer, the mond stones, followed by six strokes with (Rpk), valley depth (Rvk), core roughness recommended surface numbers for a per- a plateau brush at 20% load. depth (Rk) and highest peak to valley. formance engine with a hard block or Crosshatch recommendations also vary Many piston ring manufacturers specify a cylinders (like a typical Pro Stock or according to the application. The typical surface finish of 15 to 20 Ra for moly NASCAR motor) are: automotive application calls for a 42 to 45 faced rings, which can be achieved by fin- • Rpk = 4 to 6 degree (included angle) crosshatch, while ish honing with #280 grit stones. • Rk = 18 to 22 20 to 30 degrees is often recommended for If cylinders are honed with #325 to • Rvk = 28 to 32 performance engines. If the engine has a #400 diamond stones, the finish should be To achieve these numbers, the bores are nickle/silicon carbide coating, even less in the 22 to 24 Ra range – which is too rough honed to size with 270/325 metal cross hatch is needed, typically 10 to 15 rough for moly faced rings, so a second bond diamond stones at 170 rpm and 35% degrees. finishing step is usually necessary. Plateau load. The stones are then changed to #600 Also, don’t forget to scrub out the finishing the cylinders with #600 grit grit diamond stones and honed at 20% cylinders with hot soapy water and a stones, or a plateau honing tool or brush load for four strokes. The final step is to brush. Rinsing with solvent alone won’t will improve the finish and lower the brush the cylinders with a plateau finishing remove the metal and abrasive residue. numbers to the desired range of 20 or less. tool for six strokes at 20% load. A plateau cylinder bore finish is a good The recommended numbers for other Pistons one because it combines all the “good” types of racing such as sprint cars and drag On the outside, pistons tend to look the numbers to create plenty of area to support cars would be a little rougher: same. They are round slugs of metal with the rings, and adequate valley (crosshatch) • Rpk 8 to 10 grooves and bores for the rings and wrist pin. That is about where the similarities end, however. Today, every manufacturer has its own recipe for making a better piston, and the days of pouring a molten liquid into a mold is largely a thing of the past, at least for the performance side of things. Cast pis- tons may work fine in your vintage, mild street rod but pushing them much further than 400 horsepower will leave you with a new pile of automotive art. Today, there are numerous manufactur- ers in the aftermarket from which to choose a racing or high performance pis- ton, so it can be a bit overwhelming for engine builders who are shopping for pis- tons. But all pistons are the same, right? That statement is, of course, completely false. There’s a lot that goes into the design of a piston, whether it’s an off-the-shelf part or a specifically designed piece for a high horsepower racing application. Pistons come in all shapes and sizes from flat top to dish, domed, cast aluminum, forged, hyper- eutectic, short skirt, full round, and even asymmetrical. What you choose for your next race engine build depends on what type of rac- ing your customer does and if he or she has a budget or if there are rule restrictions

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PISTONS, RINGS & BORES

that limit your choices, because piston intake valves, a high lift camshaft or high much beyond 450 to 500 hp, forged pis- manufacturers can make just about any- lift rocker arms. tons are usually a must. thing you want. Your ring choices may also be limited The trend in piston design today has depending on the dimensions of the ring Forged been evolving for many years with pistons grooves that are available. The location of Forged pistons are made by stamping a slug being made lighter and lighter with each the wrist pin may also limit what you can of aluminum in a high-pressure die. This passing year. But today there are a number do with rod length and stroke if you want usually requires several steps. The forging is of technologies and materials at a piston to build a stroker motor, and the thickness then machined to its final dimensions and designer’s disposal to make designing a of the piston crown may limit how much heat treated to produce the desired strength lightweight piston that has enough metal can be safely removed to adjust deck and hardness characteristics. strength to last the distance and anti-fric- height or compression. Finally, stock or The alloys used to create forgings are tion properties to keep it from robbing any cast aftermarket pistons may not be strong ductile, which allows them to deform of the precious horsepower you so careful- enough to handle a significant boost in rather than crack or shatter under extreme ly assembled. horsepower. loads. In a high performance engine, this The high performance race engine by quality adds a degree of insurance because definition means that the limits are going Hypereutectic it can allow the block to survive if the tim- to be pushed to the edge for most of its Hypereutectic pistons are also cast pistons, ing chain breaks or the engine sucks a life. For piston designers, the limit is peak but are made of a high silicon content valve. The valve may beat up the top of the cylinder pressure. Maximizing cylinder alloy. The extra silicon makes them harder, piston, but the piston usually won’t break pressure will give the most gains in horse- stronger and more wear resistant so they and fall into the crankcase. power, and can be reached by increasing can handle higher loads and temperatures The grain structure created by the the compression ratio through piston reliably. forging process also improves the strength design with either a domed or flat top pis- The pistons also have a lower coeffi- and heat flow characteristics of the piston. ton or a dished piston in the case of a cient of expansion than most forged alloys, In a high performance engine, this is power adder such as a supercharger, which so you can run closer piston-to-cylinder important because the pistons have to han- dramatically increases cylinder pressures. clearances to reduce piston rock and noise. dle much higher combustion temperatures Ordinary cast aluminum stock-type Some hypereutectic pistons are made of and loads. OEM or aftermarket pistons are fine for 390 alloy and T6 heat treated to improve The two most commonly used alu- budget rebuilds and even slightly modified their strength up to 30 percent over minum alloys in forged pistons are 4032 engines. But such pistons may not be avail- untreated hypereutectic pistons. and 2618. Pistons made of 4032 are most- able in the oversize you want if you’re bor- Best of all, hypereutectic pistons are an ly designed for street performance applica- ing out the block, or the compression ratio affordable upgrade for many engines, and tions, but are also popular with many you want. The valve reliefs in the tops of typically cost 25 to 30 percent less than entry-level drag racers and sportsman cir- the pistons may not be deep enough to forged pistons. But for a motor that’s going cle track racers. It’s a durable alloy that will provide adequate clearance for larger to make serious horsepower, say anything last more than one season of racing, and

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PISTONS, RINGS & BORES

will hold up well on the street. It can also one manufacturer. handle up to 650 to 700 hp, provided the Rings High ring locations work well in stock engine has a good tune and does not go The top ring end gap is often the culprit and street performance applications, and it into detonation. whenever there are piston issues. Most top helps reduce the crevice area for lower For serious racing, the preferred alloy is land damage appears to lift the land into emissions and better fuel economy. But in usually 2618. This alloy is more malleable the combustion chamber. The reason is that really high power applications (blown or than 4032, which allows it to resist detona- the top ring ends butt and lock the piston turbocharged engines, or nitrous), many tion better than 4032. It also has a higher at TDC. Crank rotation pulls the piston piston manufacturers recommend a piston coefficient of thermal expansion than down the cylinder while leaving at least design that has the top ring somewhat 4032, so pistons made of 2618 aluminum part of the ring and top land at TDC. lower on the piston to keep the ring away require more wall clearance and make The end gap will vary depending on from the heat. They say this improves the more piston noise while a cold engine is the engine heat load when it is in opera- durability of the piston and top ring. warming up. The alloy also tends to tion. Piston alloy, fuel mixture, spark If a ring end gap is measured on the degrade more over time than high side, you improve 4032, which means the pistons detonation tolerance in may have to be replaced after a two ways: One, the season of racing. engine will run longer under detonation before Designs ring butt. Two, some leak If you’re building a high down appears to benefit revving engine, lighter is always oil control by clearing better. Lighter pistons reduce the rings from oil load- the stretching forces on the ing. A small amount of connecting rods and improve chamber oil will cause throttle response. Weight is typ- detonation and signifi- ically reduced by shortening cant horsepower loss. the length of the piston skirt The correct top ring end and using a shorter, lighter wrist gap with some pistons pin. The pistons also have to be can be 50% to 100% strong enough to handle higher more than the manufac- loads so many use box-type turer’s specs, says an struts inside the piston to rein- expert. force the skirts. Ring end gap and cylinder wall survface finish are just two of the critical fac- Ring options of The side profile of the piston tors you’ll need to account for to ensure proper combustion efficiency. 1/16˝ or stock 5/64˝ are is also important so it can han- offered in many applica- dle the heat. The top of the piston is advance, compression, cooling system tions. The 1/16˝ option reduces friction exposed to the heat of combustion, so the capacity, duty cycle and horsepower per slightly and seals better at high rpm but the upper area of the piston that undergoes the cubic inch all combine to determine an drawback is that it’s considerably more greatest thermal expansion. Tapering the engine’s heat load. expensive. Stock (usually 5/64˝ compres- side profile of the piston in slightly toward Most new generation pistons incorpo- sion rings) work well and won’t break your the top compensates for the increased ther- rate the top compression ring high on the customer’s budget. Metric ring options are mal expansion while allowing tighter wall piston. The high ring location cools the pis- also becoming more common. clearances without scuffing. ton top more effectively, reduces detona- The accumulator groove that is The location of the rings on the piston tion, smog, and increases horsepower. If machined groove between the first and is also a factor to consider. Moving the ring detonation or other excess heat situations second compression ring on some per- pack higher up on the piston improves develop, a top ring end gap set toward the formance pistons is there to stop pressure sealing and reduces the “crevice volume” tight side will butt, with piston and cylin- spikes from getting trapped between the that can trap unburned fuel and air. On a der damage soon to follow. first and second compression rings that will performance engine, a higher ring location High location rings require extra end unseat the top ring. If this happens, you exposes the top ring to more heat and gap because they stop at a higher tempera- may get ring flutter and momentarily lose increases the risk of micro-welding the ring ture portion of the cylinder at TDC and ring seal. The space created by this groove to the piston land or cylinder wall. To help they have less shielding from the heat of between the rings should be about equal to counter these effects, piston manufacturers combustion. At TDC the ring is usually the average combustion spike, keeping the may use phosphate coatings or hard above the cylinder water jacket. However, pressure low enough to prevent lifting the anodize the upper ring grooves to reduce many of today’s current designs do a better top ring while maintaining some pre-load micro-welding. job of keeping the rings cool, according to on the second ring. PPSFG

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Circle 123 on Reader Service Card for more information 24 Training_Layout 1 4/17/12 9:16 AM Page 24

IMPORTANCE OF TRAINING

these jobs the same way. The beauty is, if it hen I first started in business, does go away, it’s no big deal to me. I worked next door to a per- easier to lose his house, his credit rating and There aren’t really that many big Wson who was trying to con- develop health problems over it. changes that we can make to our business- vert a hobby into a business. He became Arguing is a lot of work and requires far es that will accomplish a world of good, but involved in a certain class of BMWs that too much mental effort. In addition, it usu- there are literally hundreds of little things all suffered premature engine failure. He ally follows you home and keeps creeping that we can do that will add up to big was adept at taking the engines apart and into your brain. Arguing with mad cus- changes in how our business operates. putting them together again, so he tomers is something you don’t have to do. I tell people who take my classes to look would quote the basic price of putting You can stop as soon as you decide you at the material as a buffet line. They will rings and bearings in the engine, call it want to. In fact, you do it by your own free find some things very appealing and some an overhaul, and take in the job. choice. things downright appalling. I ask them to However, every single one of these I was told that there are three types of take the things they like and leave the engines ended up needing far more work. men – those who learn by watching, those things they don’t. The worst thing you can The finished price to do it right was who learn by listening and those who just do is to obsess about things you don’t like. roughly four times his estimates and his have to test that it’s an electric fence them- It causes you to lose your focus. customers felt betrayed, since he had the selves. The reality is, your own “threshold of engine in buckets by the time he finally Whatever happens to be your business pain” will determine what ideas you are gave them a real total. They were literally problem, you must first decide what it is receptive to right now. You’ll like those. over a barrel and couldn’t use their vehicle you wish to fix and then find the training Other ideas you will just not be ready for or cancel the transaction. that will solve that problem. today. At some future point, you may devel- He continued to complain about “how Understand that your brain will natural- op and find a need for these. A very suc- unreasonable” all these customers were. He ly be resistant to any new ideas, even if cessful shop owner will find most good said they should understand that it just was- they’re good. You’re generally most recep- ideas have been implemented and the pick- n’t possible to know if extra work was tive when you reach the “threshold of ings are slim. If you can take a 2-week vaca- needed ahead of time. But after a few very pain” that pushes you over the edge. Once tion and find the place humming right unpleasant confrontations with very you realize that you will be skeptical and along, with no problems and record sales unhappy owners, he should have figured you will resist new thoughts, it will be eas- for the period when you return, you are out that he wasn’t doing these estimates ier to begin to look for ways the idea will where you want to be. correctly. Since nearly every one of these work, rather than ways it won’t. We all Until then, think about where your did need the work, he should have advised know that getting a shot hurts but we thresholds of pain might be and seek out them of that possiblity in advance. That way accept it because it will make us better. some possible solutions to evaluate. he could avoid “the big surprise.” Often false beliefs are our worst enemy. Training is available at live conventions or Despite complaining to me constantly I once believed that doing major engine events, live sessions led by an Instructor, and ignoring my suggestions, his approach work was not profitable, because I couldn’t DVDs, magazines or online. A good shop grew grim and he came to regard his cus- charge enough. Others in the industry sug- will constantly be evaluating what goes on tomers as adversaries, who were just out to gested that I price the work so that it paid and how it can be done easier. No one can get him (He actually turned out to be the same per hour as replacing brake pads. afford to exist without change and no one right). He never learned a thing and he was So, I did that and the estimate for simply has it all figured out. Once you figure that forced out of business. It wasn’t that he installing a rebuilt engine was very high, out, you can stop learning about electric couldn’t learn, it was that he wouldn’t learn. but it paid the same per hour as doing fences. PPSFG People like this may say that they have brake work. I made it even higher by 10 years experience, but the reality is, they including extras that would come up, like a Becky Witt, AAM, is nationally recognized as a just got one year’s experience 10 times. new water pump, oil seals, thermostat and leading industry expert. She is a real repair shop They never got past the basics. so on. It was substantially more than I’d owner, who talks to customers every day. She is What is so difficult to comprehend ever thought it would be, and the customer an approved instructor for the Automotive about evaluating the possible things that still said yes. Management Institute (AMI) and has earned might go wrong with a job, totaling up I was stunned that I got the job. I ratings as one of their most popular instructors. what that might cost and advising the cus- learned that sometimes you price a job that Her innovative solutions to complex problems tomer of those things ahead of time? you don’t want to do so it will go away – if make real-world sense and are easily learned and My shop neighbor seemed to think that it doesn’t, it pays enough to make you want implemented. She is best known for being very this was too difficult to learn and that it was to do it. Through the years, I’ve sold a lot of entertaining and throwing donuts.

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Circle 126 on Reader Service Card for more information