3.6 track engine

[r lane]

I am building a 3.6 track motor. The CR with .040'' being the deck gap is 11.8-1.0. My deck gap or piston to head clearance on this motor is .060''. So my CR will be less than 11.8. Also I am going to have to cut the intake pockets on the pistons .070'' as I don't have the valve to piston clearance that I need. That drops the CR additionally. To get the deck gap to .040'' bringing the CR up some, will require my cutting the cylinders. Don't know what the desired magic CR should be, but of my two 3.0 motors, the one with the higher CR definitely has more pop. My thoughts/questions; #1, how important is getting the piston that close to the head creating what I have heard called the ''squish'' factor. #2, I can cut the cylinders on either end. At the bottom will require my also cutting the O ring groove. At the top will require additional milling on the surround area of the head so that the cylinder fins don't bottom out. Also the CE ring groove will have to be cut. Is the CE ring needed. Was intended to stem oil leaks I think. any info with experience in this area would be greatly appreciated. Thanks, Bob

[icarp]

Bob
#1 , how important is getting the piston that close to the head creating what I have heard called the ''squish'' factor.
You are building an engine for racing .... Squish is paramount .... .039" to .036" reliable .

The pistons that you have are not correct for your engine ...... Have a custom set made .

Just my thoughts
Ian

[PeteKz]

Emphasize what Ian said. Squish increases combustion chamber turbulence, which increases fuel mixing and flame propagation. It's not only important for racing engines, but for street engines, and for the same reasons--it makes the engine more efficient. In street engines I shoot for .030", and for low-rpm engines, I'll go lower, say .025" or even .020". People tend to think that the limit is stretching of the rod at high RPM, which will cause the piston to kiss the head, but IMO, a bigger concern is that the piston rocks across the wrist pin as it goes up and down. If you have very tight piston to cylinder clearances (and Porsche engines with aluminum pistons and cylinders do have tight skirt clearances), the piston will rock less, allowing you to run a tighter piston/head clearances.

However, since you are building a race engine, stick to what Ian recommended,

[Henry Schmidt]

Racing formulas teach us the theories for maximum performance but in amateur racing, maximum performance has it's limits.
Amateur drivers make shifting errors, engine operation oversights and maintenance decisions based on budget.
Close tolerances cost money and challenge reliability. In every racers budget there are compromises and keeping to a regimen of "racing" tolerances will often cost seat time. The greatest advantage an amateur racer can buy.

[Henry Schmidt]

Robert, I noticed you called about Supertec head studs. They fly off the self as quickly as we can produce them. We have one set on reserve for you. I'll try to call you on Tuesdays.