What is my compression ratio considering this..

383 stroker
flat-top pistons w/ -4CC valve reliefs
Block was true decked
.039" gasket
heads are stock CC's (54)

Thanks

Cody

 

You don't give enough info for an exact answer, especially what you mean by "true deck". If that means zero deck, the CR is ~12.7:1. Go to http://www.smokemup.com/auto_math/compression_ratio.php for a good on-line CR calculator.

Rich Krause

 

Hmmm..its saying I have to have a log in to use that calculation...

My engine builder True Decked the block so Im assuming it was 0 decked..I didnt think I was running that high of compression

Cody

 

The site is worth registering for (free). AFAIK there is no downside. has some great auto math calculators. There's another that is a litle less comprehensive at http://www.rosspistons.com/CR%20Calculator.htm

Rich Krause

 

Well unless Im mistaken, if he had to deck the block, then it is not zero. Unless there is someway to add material and mill it. If he decked it at all it will be less than zero deck. Im guessing by "true deck", if thats what he told you, that means he decked it so it was flat again. So find out what the deck height is and check out one of those calculators to find out exactly, but remember, that is just static compression, there are tons of other variables to factor in to find out the dynamic compression which is all that really matters, you could run 14 to 1 on pump gas with the right cam setup.

 

The deck could be anything, as the term "true deck" is not in widespread use. Obviously, the actual deck will depend on the deck height, rod length, and compression height of the piston. If it has a positive deck, there may be a problem with clearance using 0.039" gaskets. Most people set up steel rod motors with ~0.040" piston crown to cylinder head clearance. That gives a good "quench" without risking interference. Some engine builders go as close as 0.035" when using a light weight piston/rod combo.

Rich Krause