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Thread: 390 to pump gas

  1. Tue Apr 01, 2008, 05:55 PM #1
    74390
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    390 to pump gas

    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.
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  2. Wed Apr 02, 2008, 05:25 PM #2
    Big Bad AMX
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    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/American...hread.php?t=98


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