VALVE SPRINGS BY MIKE MAVRIGIAN In this article, we’ll try to cover the the spring can travel before reaching basics of performance valve springs, coil bind. If installed height increas- in terms of dimensions, selection ad- es, spring tension will decrease, but vice, handling precautions and more. the spring travel will increase before Consider this somewhat of a basic reaching coil bind. overview of valve spring technology. The valve spring needs to have enough travel (from closed-valve INSTALLED HEIGHT, OPEN installed height to a safe margin PRESSURE AND COIL BIND before coil bind) to suit the valve Valve spring installed height refers lift created by the camshaft lift and to the dimension measured from the rocker arm ratio. The safety margin bottom of the spring retainer (where (full travel before coil bind) should the top of the outer spring contacts be kept at a minimum of 0.060”. the retainer) to the spring pocket in Valve spring open pressure the cylinder head, when the valve is represents the pressure (in psi) that’s closed. placed against the spring retainer Installed height affects spring at maximum valve lift. You need tension, and is the determining fac- enough pressure to control the lifters tor of what the spring closed tension as they accelerate up the cam lobe will be. The camshaft specification and when decelerating when ramp- card will list the suggested spring ing down past the lobe peak (when installed height for that cam with the the valve changes direction from cam maker’s recommended springs. opening to closing). If the spring For example, if the card notes that doesn’t provide enough open pres- a specific valve spring part number sure, the lifter can bounce over the should be installed at 105 lbs at cam lobe (valve float), resulting in 1.700”, that means that if the spring the lifter smacking into the closing is installed at a height of 1.700”, this ramp of the lobe, potentially reduc- should place 105 lbs of tension with ing cam lobe and lifter life. the valve closed. Never assume that Open spring pressure is a func- this is correct. Always check this on tion of the combination of spring a bench-mounted valve spring tester. rate, net valve lift and seat pres- Changing installed height will sure. Excessive open spring pressure affect spring tension. If you need results in stresses placed on the to reduce installed height, you can pushrods and in turn, valve bounce. place a shim (of the needed thick- Lighter valves require lower spring ness) under the spring, or you can pressures, which reduces the risk of use a different design retainer with a pushrod flexing. shallower dish (using a retainer with Valve spring coil bind takes place a deeper dish will increase installed when the spring is compressed to a height). You can also use a valve point where the coils contact each lock that id designed to change the other. You can measure coil bind retainer height location. height by placing a retainer on top As the installed height is de- of the spring, and compressing the creased, spring tension will increase. spring (carefully) until the coils This also reduces the distance that touch each other. The distance from 18 APRIL-JUNE 2015 engine professional EP Q215 1-96.indd 18 3/20/15 10:09 AM Example of basic valve spring layout and applicable dimensions. (illustration courtesy PAC Racing Springs) Example of coil bind determination. Installed height of this spring is 1.950”. When we subtract combined valve lift (minus lash) of 0.785”, we determine a coil bind height of 1.105”. This provides a safety clearance of 0.060” to avoid coil bind. (illustration courtesy PAC Racing Springs) the bottom of the retainer to the bottom the cylinder head (remember to dedicate of the spring is the coil bind height. each valve to each valve location in each Subtract the coil bind height from head…that way, once measured and the installed height. The result is the clearanced, you know that the particular maximum spring travel. The standard valve will fit properly in a specific loca- recommendation to provide a safety tion. Don’t assume that you can mix up margin is to have a minimum of 0.060” the valves). With the valve fully inserted spring compression travel greater than into the (intake or exhaust) location, the full lift of the valve. If the coils bind, with the valve fully seated, install locks this creates a dead-stop during valvetrain and the retainer. Pull up on the retainer operation, so something’s gotta give, in- and measure the distance between the un- cluding potential pushrod bending, lifter derside of the retainer (where the spring or cam damage or rocker arm failure. contacts the retainer) to the spring seat. The use of a bench spring tester offers If you’re using hardened spring seats, be a convenient method of pre-determining sure to install for this check. coil clearance. Reference the spring’s Remove the spring from the head and installed height. Install the valve into place the spring on the tester. Compress www.engineprofessional.com 19 EP Q215 1-96.indd 19 3/20/15 10:09 AM valve SPRINGS BY MIKE MAVRIGIAN This valve features a square-cut groove. Only a square-key lock will work here. Never assume that your locks (keepers) are correct for the valves at hand. Installing the incorrect style locks will lead to disengagement (locks This valve features a radius lock groove. You need to pay attention to this. Only and retainers popping off), which can lead to a very quick catastrophic valve a “beadlock” style lock (keeper) will work with this type of groove. failure, including bashed pistons. This closeup shows a typical beadlock style valve lock. Only use this style if This is a square-cut lock. Again, this will only work with a valve that features a the valve features a radius groove. square-cut groove. This may sound very basic, but it’s easy to make a mistake if you’re not paying attention during valve/spring assembly. to the afore-measured height. The pres- duced cylinder pressure (reduced power) pressure and/or oil thickness is increased, sure tester will display the seat pressure but this can also result in deforming valve spring pressure must be increased at that installed height. (tuliping) the valve head, to the point as well in order to maintain lifter control Reference the maximum (gross) lift where the head can actually snap off of and to prevent pumping up. So, if your of the valve, based on your cam lift the stem. engine is supposed to use, say, 10W-30 and rocker arm ratio. The difference With hydraulic lifters, the springs oil and you move up to a straight 50W between the two measurements should need to place enough pressure at the oil, you’re not doing the engine any indicate how much additional travel is valve lifter to keep the lifter plunger cen- favors. Thicker is not always better. available to the spring. For example, if tered in its travel to prevent lifter “pump A common misconception involves the installed height of the valve spring up.” Pump-up causes the valve to be the belief that higher spring pressures is 2.000”, and the maximum lift of the held slightly off of its seat, which reduces reduce horsepower, due to the increased valve is 0.5000”, the open spring height power and can also be mis-diagnosed as resistance of the springs. What we need should be 1.500”. a misfire (with resulting misplaced blame to bear in mind is that for every valve Sufficient seat pressure is needed to on the ignition or fuel system). that is opening and the spring being com- keep the valves from bouncing when Unnecessarily high oil pressure and/ pressed, another valve is closing and its they return to their seats (valves closed). or higher-than-necessary oil viscosity valve spring is expanding. This expansion Bouncing valves results in not only re- can cause hydraulic lifter pump-up. If oil force actually returns the energy to the 20 APRIL-JUNE 2015 engine professional EP Q215 1-96.indd 20 3/20/15 10:09 AM Engine-Professional-2015_Q2 2/24/2015 2:42 PM Page 1 valve SPRINGS BY MIKE MAVRIGIAN valvetrain and the engine, resulting on Hydraulic roller cams/lifters require can use springs in the 450 lb range Ensure zero horsepower loss. This phenomenon higher spring seat pressures in order to (again, here we’re referring to also ob- is referred to as the valvetrain’s regen- control the heavier roller lifters, as well taining decent valvetrain life/durability). erative characteristic. In short, when in as to control the more aggressive opening Open spring pressures that exceed doubt, run slightly more spring seat pres- and closing rates common to roller cams. 360 lb open pressure should really be Maximum What sure, not less. Small block engines generally require mated with billet steel roller lifter bodies seat pressures in the 120 –145 lb range. (not OE-level cast iron roller lifter bod- is coil TIPS ON CHOOSING VALVE SPRINGS Big block engines usually need seat ies). Flat-tappet cam/lifters for street and pressures in the range of 130 – 165 lb. Solid lifter roller cams/lifters are Performance bind street/strip: General-purpose street small block generally reserved for race applications Small block engines will generally engines with hydraulic roller cams or “serious” street/strip use. Solid lifter and require 105 – 125 lb seat pressure require at least 260 lb open pressures roller cams are designed with more aggressive opening and closing rates, re- With Valve how is it measured? Big block engines (due to heavier for applications up to about 4000 valves) usually require 115 – 130 lb seat rpm.