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How do you build a 1000hp 4G63?

23 December 2014

We asked STM’s Andre Simon, who built Michael’s engine, how you actually build a Mitsubishi 4G63 capable of 745kW/1000hp, and why Michael’s previous forged engine isn’t up to the task. 

He says: “The main difference between the two engines is the internals, particularly the strength of the con rods. Michael’s new engine is built with Carrillo H-Beam con rods, which are widely regarded as being some of the strongest on the market. We considered aluminium rods, which is what we fitted to Project DS9 [the STM-built Evo IX drag car driven by David Stock and featured on the cover of NZPC Issue No. 61 in 2010]; however, they have a run life of approximately 50 to 70 passes at full power, and we deemed the maintenance to not be worth the advantages.

“The con rods are custom built and are 6mm longer than a factory rod to improve the rod-to-stroke ratio. This becomes important when we start running to 10,500-plus rpm. The difference in the rod length is taken up by raising the wrist pin height in the JE pistons, so that the deck height is still correct and the pistons don’t protrude out of the block.

“The pistons are our own design and incorporate the features we have developed over the years of developing these engines. First of all, the pistons raise compression to 10.5:1, which is better suited to methanol or E85 use. We also have deeper valve pockets that offer sufficient clearance for our aggressive high-lift high-duration drag cams. 

“As I mentioned, the pin height is raised to accommodate the longer con rod, and we selected a heavier-duty wrist pin with a thicker wall to resist bending under high boost / high rpm use. The ring set is also custom, and utilizes a ‘gapless’ top ring to improve cylinder sealing and reduce blow-by. To aid ring seal, we also use vertical gas ports in the piston crown that allow combustion pressure to get behind the top ring and push it out, promoting a better seal.

“The bottom end has been fitted with an aftermarket forged crankshaft for the best possible reliability. While we have proven with ‘DOCILE’ [Andre’s famous Evo III drag car] that the stock Mitsubishi crank can handle 1000-plus whp and 11,000rpm, it is also prone to cracking under this type of use, so we opted to go with an aftermarket crank for increased service life.

“The head-gasket system is probably the only other real change in Michael’s new engine. This becomes the limiting factor with any high-boost import engine, and we have adopted a new technology here. The head gasket consists of special sealing rings that are keyed into the deck surface of the block around each bore. Beyond these rings, the oil and water are sealed by a conventional copper gasket. 

“Right now, the power potential of the engine is held back by the small turbo and the mild cams; however, once Michael has the car dialled in, all we need to do is step up the turbo to a Garrett GTX4508 and fit a set of our drag cams, and 1000-plus hp will be a walk in the park.”