What kind of compression ratio

StadEMS3

Dirt-Old 20+Year Member
Jun 19, 2003
228
43
49
Mechanicsville, MD
I was wondering what kind of compression ratio I was running for possible super charger install. I know I seen a thread on here not to long ago about it. This is what I have:

Stock block bored 0.30 over
AFR 165 heads:
60cc combustion chamber
DSS 331 stroker kit:
-33cc flat top pistons
5.315" I beam rods
3.25" stroke on the crank
FRPP 6051-A302 head gasket
.042 compessed thickness
4.100" bore

I came up with 11:1? :shrug: A little to high for a supercharger? Any suggestions? I guess I need to ditch the Cobra intake too for a little more HP/TQ.
 
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as far as i know there is not a quick cheap fix for compression ratio.

other than larger cylinder head chambers, and dish pistons are going to be the main fix's

a thicker head gasket might lower the compression a hair but nothing worth going through that much trouble
 
After posing the question on Sport Trac site I hang out on, they came up with 7.6:1 C/R...with a 0.0 deck height. I went back and checked my numbers and all was good, BUT I neglected to click on the "calculate C/R" button!! I thought it was calculating while I was inputting numbers :doh: I have no idea what my deck height is, but I don't think it would be getting me close to the 11:1 like I thought I was at...

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

I guess I'm good for a supercharger!!!!
 
you might wanna check on your pistons.

-33 cc's for a flat top piston sounds funny to me as the -33 would suggest dish pistons and not flat top.

using that calculator and an average piston to deck clearance of -.005 i came up with a shade under 8-1 compression.

assuming all your information is correct i see no problem running boost on your engine on pump gas.


i would suggest a good dyno tune calibrated to whatever octane you have available to you
 
fingers faster than brain: -3cc, they are flat top with valve relieves. Now I'm back up to 10:1. I don't know the stock cylinder bore with a .030 over measurment would be. This is taxing my brain to much with all the numbers... lol