Engine Build / Stroker before FI - Thoughts and Questions

Originally Posted by Mike@GTM

I'd like to add a few things in here if I may.

The main reason people are concerned with piston speed is not so much the actual speed itself, but the derivative of it (velocity more specifically): acceleration. At top dead center on the exhaust stroke, the piston has to come to a complete stop and reverse direction with no resistance from any gas in the chamber working against it. That puts all the load on the connecting rods. The lower the rod ratio is, the higher this acceleration is at TDC. Generally, people look at a lot of documentation pertaining to OEM limits on piston speed. However, one of the factors in all this is the mass of the piston itself as well as the materials the connecting rod, wrist pin and piston are made of. The higher the tensile strength of the connecting rod, the higher the acceleration can be before the rod starts experiencing fatigue.

The bottom line here is that when we designed our stroker kits, we made sure that the tensile strength of the billet chromoly rods was high enough to withstand the inertial loads generated by the rod ratio at redline as well as the mass of the pistons we use. Also, there is a limit on how high you can rev the stroker engine. Basically, you should not rev it beyond the stock redline for maximum longevity.

One of the many advantages of our stroker kit is the oiling system in our crankshaft. We use a straight shot oiling system as opposed to the factory cross drilled oiling system. The straight shot oiling system improves oil flow to the rod bearings at high rpm while the centripetal forces in the cross drilled crank makes it more difficult for the oil to reach the rod bearings at high rpm.

All that said, when planning a build, it is important to recognize that you have to specify the compression ratio when you build the engine. That means if your plan is to build a forced induction car, you'll need to specify a lower compression ratio. The flip side is that if you do that and don't put a forced induction system on the engine, it'll be a complete dog as a naturally aspirated setup. At the same time, if you decide to go higher compression and then end up putting forced induction on there later, down the road, then you won't be able to run the turbos/superchargers at higher boost where they are more efficient and flow the most air.

Typically, if you have to choose between a built motor and a forced induction kit, I recommend getting the forced induction system first and doing the built motor later on. That way, you can enjoy the additional power on a stock engine then crank it up once you've built the motor and gotten all the additional supporting modifications for the extra horsepower.

Just my $0.02