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Cap206

11-10-2005 05:38 PM

Compression formula

Trying to find what cc heads I need to make 9:1 on 383sbc.
4.030 X 3.75 stroke.I am useing flat top pistons

jmherbert

11-10-2005 06:08 PM

Re: Compression formula

Check this site out

http://midwestmotorsportsinc.com/tech_calc.php

formula31

11-10-2005 10:21 PM

Re: Compression formula

http://not2fast.wryday.com/turbo/com...pression.shtml

This ones a little more accurate.

Liberator21

11-10-2005 11:02 PM

Re: Compression formula

How far down in the hole are the pistons sitting?

Cap206

11-11-2005 12:08 AM

Re: Compression formula

I am not sure of deck height,I bought short block from a freind who didn't finish.All I really know is it has TRW forged flat tops with 2 relief cuts on 5.7 rods.I'll have to get more info out of him.I was looking at World S/R heads,they make a 76cc chamber,I think I will need big chamber to offset flat tops.Happy to here all opinions

Pat McPherson

11-11-2005 03:08 PM

Re: Compression formula

Flat tops, standard deck height, standard head gasket, 76cc chamber should be right around 9:1 for 350 with 3.48 stroke.
With a 3.75 stroke, I would guess you would be closer to 10:1.

Liberator21

11-11-2005 04:07 PM

Re: Compression formula

If the heads are off, measuring the piston is easy. If you don't have a depth mic, bring a piston up to TDC and put a straight edge on the block across the piston bore. Then, take a feeler gage and measure the gap between the piston and the straight edge. That will give you a measurement you can use. Then the compression calculation is easy.

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