ok... i have tried calculators on the net.. and they are all telling me my compression is going to be insanely high.. (ive got to be doing something wrong..)



engine is a 408, heads are 64 CC, i will be using cometic .041 gaskets, and my pistons in the 408 have an 8cc dish. how do i figure out the damn compression ratio?? anybody know roughly where ill be??

 

You didn't mention the deck height (how much the piston is in or out of the hole) which is critical when calculating static compression. The calculator listed below is considered very accurate because it correctly factors this into the equation.

http://www.rbracing-rsr.com/compstaticcalc.html

Here's a couple for dynamic compression.

http://www.kb-silvolite.com/calc.php?action=comp

http://www.rbracing-rsr.com/comprAdvHD.htm

Check out the Advanced Performance Tech forum here. There are a couple threads about all of these topics.

 

the shortblock is zero decked.

 

ok i just did that and im coming up with 13.99 compression ratio!!! how is this possible??? what am i missing/??

 

nevermind... its 11.11.. i was putting in a negative for my piston when it was supposed to be positive..

 

Yeah, it seems backwards, but think of it as: "a positive sign means addition, so it adds to the chamber volume.."