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Old 04-14-2009, 07:54 AM   #1 (permalink)
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S&S 113 compression PSI

OK, I sent my 113 heads out to Robbie McCay, he did a port job and put in new valves. Took .030 off the deck, and Im running ..030 head gaskets. (Stock was .048 and had, according to S&S 10.1 compression.) 0 piston deck height.

Im running the S&S640 cam, and I figured that with taking .030 off the heads and .018 out in gasket, my CR should be about 10.8.

When I do a ccp test I get 170-175PSI, is this about right?

Thanks
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Old 04-14-2009, 07:35 PM   #2 (permalink)
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Quote:
Originally Posted by TonyJ View Post
OK, I sent my 113 heads out to Robbie McCay, he did a port job and put in new valves. Took .030 off the deck, and Im running ..030 head gaskets. (Stock was .048 and had, according to S&S 10.1 compression.) 0 piston deck height.

Im running the S&S640 cam, and I figured that with taking .030 off the heads and .018 out in gasket, my CR should be about 10.8.

When I do a ccp test I get 170-175PSI, is this about right?

Thanks
I cant directly answer your question, but i will tell you this, psi in the cylinder doesnt directly correlate to compression ration, simply because of camshaft profiles, duration, overlap and all that stuff, my buddys 12.5 to 1 468 only has 200 psi cranking compression, because of the huge overlap. hope that helps.
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Old 04-14-2009, 08:03 PM   #3 (permalink)
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When I do a ccp test I get 170-175PSI, is this about right?
A 640 in a 113 with a mechanical cr of 10.8 would be about 182-183 psi at sea level. You're probably at about 800ft above sea level, so that would be around 178-179 psi. So if your gauge is accurate, 173 psi is about 10.6 mechanical.
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Old 04-14-2009, 08:35 PM   #4 (permalink)
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Thanks for the info guys. I will get my hands on a better gauge and recheck, but this atleasts lets me know its not too far off, and now I can sleep again at night. Really.

Thanks again.
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