12-28-2004, 06:19 AM
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CC Member
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Join Date: Mar 2003
Cobra Make, Engine:
Posts: 1,515
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Ken - 140psi at 10.7 Compression! Who built your motor? I've never heard of it being that low.
Scott - Your 120 readings are definetely low. typical set-ups and 10.5:1 compression should yield about 160 psi - give or take a few. Like SOBRAC, mine at 11:1 were all at about 190 - which is what you'd expect. Let me know if I can help you do a leak down test - just come up to the house as I still haven't gotten that ride. 
A common mistake is putting the wrong pistons with 427 heads which have the 86 cc combustion chambers vs 72 cc . By putting 10:1 pistons (like you stated) your compression will be down in the 8's - probably 8:5:1 or so. To yield 9.5 compession your PISTONS would need to be 11.5:1 to offset the large chambers on medium riser heads (Shelbys are based on these). Good luck!
Last edited by Cracker; 12-28-2004 at 06:21 AM..
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