Page 1 of 1

Anyone know how to figure compression ratios?

Posted: Sun Mar 25, 2012 3:49 pm
by markmitchinnh
The engine I am putting into my Safari is a 1996 Chevy 5.7 from a tahoe. The stock compression ratio was 9.4 from the factory. The changes I made to it: basic re-ring kit. New oil pump, cam and bearings, And the big one is the cylinder heads: 1998 5.0 vortec heads with 194/150 valves
rebuilt and shaved .15000 . Now I understand I would get better overall performance with 5.7 heads but this is a temporary situation until I finish the 355 I am building for possible end of summer installation. I would like to know possible compression ratio so if I need to I can order thicker head gaskets. Thank you, Mark

Re: Anyone know how to figure compression ratios?

Posted: Sun Mar 25, 2012 6:56 pm
by Smiliesafari

Re: Anyone know how to figure compression ratios?

Posted: Sun Mar 25, 2012 7:13 pm
by 1Gary
Mark-there are two ways to look at compression ratios.The first link is for SCR or static compression ratios:

http://www.csgnetwork.com/automotiveconverters.html

That is for setting up deck clearances,piston choices,head choices,etc.

The second one is dynamic compression ratios which takes into account cam choices and the amount of overlap and how much compression is bled off during the time when the exhaust and intake valve are both open.

http://www.wallaceracing.com/dynamic-cr.php

http://www.wallaceracing.com/eff-cr.php

Your going to need to know the deck height,piston cc(btw< -> means less displacement of a piston in the chamber as a example a dished piston.),the bore size,rod length,stroke,gasket thickness compressed,head cc.

Re: Anyone know how to figure compression ratios?

Posted: Mon Mar 26, 2012 4:01 am
by markmitchinnh
ok Thank you