Hi Guys,

A few questions just to get some different views -

When I first got my engine built I was told it had 9.85:1 comp. It is a 406 with forged TRW flat tops, Felpro gaskets, 72cc Sportsman 2's & the block has been decked but not sure how far. Heres the questions -

I have a number for the pistons that are in my engine but because they are so old I cannot find any info on the size ( cc ) of the reliefs in them. They are a TRW flat top plus 30 ( TRW L2489F ). Does anybody know how big the reliefs are in these pistons ?

What is the thickness of a Felpro gasket, I have read about 40 thou but not sure on this ?

If I am currently running at 9.85:1 comp & the engine is making about the 430HP mark, by bumping the comp up to about 10.75:1 what sort of power difference will this make ? I have read things that say the difference between a 10:1 engine & an 11:1 engine making roughly 500HP is about 20 HP but once again not sure on this ?

With my current heads 72cc on a 4.155" bore, 3.75" stroke, I am at 9.85:1 comp, when I order my new aluminium heads, what size chamber do you believe I will need to get me up near the 10.75:1 comp area ?

It's been written that every increase in CR by one point raises power output between 3 and 4 percent and the higher you start from, the lower the output increase.

In other words, going from 8 to 10 will produce more overall power than going from 11 to 13 to 1CR.

I use this CR. calculator site...

http://www.campbellenterprises.com/Race%20math%20calculators.htm

.040" headgaskets, a DITH piston of a stock .025", -5 cc valve notch w/ 76 cc heads creates right at 9.73 to 1.

You need to take a head off and cc a piston top, mic your headgasket for thickness and measure the piston DITH so you know what you will need.

Sorry, no easy way here, imho...

pdq67

PS., and I would set my next quench distance between .035" and .045" and adjust CR. using the chamber volume!!