74390
Tue Apr 01, 2008, 05:55 PM
Looking for info on getting a 68 390 AMC motor down to a pump gas friendly C.R. (roughly 9.2 ratio). Need C.C. of 401 heads and 390 also.
Big Bad AMX
Wed Apr 02, 2008, 05:25 PM
You'll need to drop into the eights to run 100% premium pump gas safely. My AMX is running a 9.6 compression ratio and I still run octane boost. I would run boost with a 9.2 as well.
The stock '68, 69 390 heads have 51cc chambers. The 401 heads are 58cc.
You'll find quite a bit of information in this thread including putting later dog-leg heads on an early block:
http://www.amx-perience.com/AmericanMotorsForum/showthread.php?t=98
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