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How To Build a High Performance Cummins Diesel HOW TO BUILD A HIGH-PERFORMANCE CUMMINS DIESEL ENGINE By Bruce C. Mallinson CEO/ Diesel Injection of Pittsburgh Keep in mind while reading this document that it is a gathering of all the articles Bruce has written over the last ten years. There may be some old prices discussed so, to get the latest pricing, check the main page. If you have any questions feel free to call us at 724-274-4080 and we can discuss your horsepower needs. Please have your CPL#. If you are looking for upgrades for your Electronic Celect/Celect Plus Cummins engine visit our Pittsburgh Power site at Pittsburghpower.com. HOW TO BUILD A HIGH-PERFORMANCE CUMMINS DIESEL ENGINE This is a very controversial subject and 99% of the mechanics who build diesel engines will disagree with what we have to say and will probably refuse to build the engine for you. For the owner-operator who loves horsepower do not give up when you speak to the negative mechanic. There are a few good shops throughout the states that will build the ultimate performance engine. Or you can build it yourself as long as you have mechanical knowledge and tools. BUILDING THE ENGINE: In order to have the engine live with high horsepower and run efficiently you must have the right combination of compression ratio, fuel, air and timing. Please do not try to get extreme power simply by increasing the fuel pressure on a stock engine. You will obtain some horsepower, however your compression ratio, air and timing will be wrong. The best time to obtain horsepower is during a rebuild. Since you are going to buy new parts anyway you might as well buy the right combination that produces horsepower and generally the price of the high performance parts is the same as the stock parts. NOW TO THE NUTS AND BOLTS : The compression ratio of the pistons and the timing must go together. High compression pistons belong only in gasoline engines that are naturally aspirated. Turbocharged diesel engines must have low compression pistons in order to produce high horsepower. The lower the compression ratio the less wear on rod bearings and the lower the internal pressure will be when the injector fires. High internal pressure is very detrimental to the life of a piston. When you see a piston with a hole burned through, it's not the fault of the injector it is a result of internal pressure. To control the pressure we lower the compression ratio and retard the timing. If you compare the compression ratio and timing of an NTC 290 versus an NTC 400 you will see the difference. Where do you think we have to be on the timing to produce 700 horsepower from an NTC? All NTC Cummins engines manufactured after Sept. of 1987 were cut for the LPF liner. If your engine was manufactured before Sept. 1987 you will have to have your block machined to accept the LPF liner. The price to cut the block in the chassis is approximately $450. The advantages are as follows: (1) The liner is now a press fit into the block and held more securely (2) With the liner being held tightly in the block you eliminate seeping head gaskets (3) Eliminate liner cavitation or liner pitting (4) Eliminates blow-by. This may sound absurd however, when the injector fires, the pressure distorts the liner until it comes in contact with the block. Your piston rings stay perfectly round and now, with the distorted liner, the rings lose contact with the cylinder wall and thus you have blow-by. Lower press fit liners help to eliminate this distortion and (5) Eliminate cracking of head bolt-holes. With LPF the pressure from the liner is moved down in the block by approximately 3\8&";. Please keep in mind that if the surface of your block is rough and should be resurfaced, remove it from the chassis and have it resurfaced. Inspect the block Page 1 How To Build a High Performance Cummins Diesel for cracks from the head bolt holes into the counterbore area. The cracks are hard to see and can be repaired by having head bolt hole repair sleeves installed. The water holes can also corrode and crack. Salvage sleeves, too, can repair them. To build a strong running engine you must start with a good foundation, which is your block. If you ignore block problems they may come back to haunt you. TURBOCHARGERS : One of the most important components on the diesel engine is the turbo. Many trucks come equipped with a 3-series Holset turbo. That is fine for stock engines. The 3-series Holset is adequate for engines up to 450 horsepower. For higher horsepower you must have a 4-series Holset. Preferably one with a mapwidth enhancer. The mapwidth enhancer consists of the 3 slots in the compressor housing that allows more air to the lower fin. With dual exhaust and dual air cleaners it is possible to obtain 42 to 45 lbs. of manifold pressure. PISTONS : When building an engine that is turbocharged you must lower the compression ratio when increasing the horsepower. The efficiency gained from increasing the manifold pressure will more than compensate for the compression ratio. Cummins also offers a high strength piston that we have ceramic coated on the top and Teflon coated on the skirts. The ceramic coating helps to keep the heat out of the piston and in the combustion chamber where it can further help to burn the fuel. The cooler we keep the piston the longer it will live. The Teflon coating on the piston skirt helps to remove the piston slap on the side of the liner. Teflon is the most slippery substance known to man and will allow your engine to more smoothly and quietly. TURBINE HOUSINGS : Many people believe that going to a larger turbo will give them an increase in power. The problem with this change is that the turbine housing of the turbo is also much larger. Which, in turn, decreases the amount of backpressure in the engine. This is good because it allows the engine to run more freely, but with the loss of manifold pressure. The engine will run much hotter. As the size of the turbine housing increases the speed of the turbine wheel and shaft decreases manifold pressure also decreases and the response time or turbo lag also increases. All are negatives. When purchasing a larger turbo you must find out how many sizes of turbo housings are available for the particular turbo you are choosing. The larger the compressor wheel (fresh air side) the greater the volume of air available to the engine. Now, you must be able to spin the larger compressor wheel at low RPM and to do this you need a smaller turbine housing on the exhaust side to increase the velocity on the exhaust. The sizing of the turbine housing effects the speed of the turbine wheel and how fast the wheel comes up to full speed the same way lower gears in your differentials effect how fast your truck can accelerate. If you live mostly in high country (5000 ft. elevation or greater) you will want to decrease the turbine housing size one step lower than if you lived at or near sea level. CAMSHAFTS : The big cam I, II and III engines all used the same basic camshaft except for the flange and flangeless design. However, the lift of the injector and valves were the same. The big cam IV 400 camshaft did have more lift to the valves. Therefore, you must use a B.C. IV piston with deep valve pockets so that the valves will not hit the pistons. Please be careful when working with a big cam IV. For building horsepower we prefer to use the high-lift cam along with the mechanical variable timing. This particular cam has .266 inches travel to the injector where the standard cam has .224 inches travel. The longer the travel of the injector the greater the amount of fuel can be injected. Fuel makes horsepower and you need a lot of it to produce 700 to 800 HP. Manifold pressure or turbo boost burns the fuel to produce the power. However, all boost and little fuel will give you little horsepower. You must get fuel injected and atomized into the combustion chamber to produce power. MECHANICAL VARIABLE TIMING : MVT has a very poor repore with mechanics of Page 2 How To Build a High Performance Cummins Diesel Cummins diesel engines. The main problem was that the steel piston in a cast-iron bore that was moved by compressed air from the air compressor would rust to the walls because of lack of lubrication. We now have an automatic oiling system that constantly lubricates the piston which makes the MVT almost trouble-free. The advantages to this timing system are many but the first and most important benefit is decrease white smoke when the engine is idling or cold. With the mechanical variable timing your engine idles in the advanced mode and when you accelerate the timing will change to a retarded setting. The retarded mode is great for making power and the major benefit of this is piston and rod bearing life. Retarded timing is much easier on the engine components than fast timing. Many of the mechanics that work on Cummins engines do not understand the MVT and may not be able to set the timing properly.

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