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Too high compression

July 10 2012 at 3:33 AM

Barry R  (Login Barry_R)

Response to Compression calc please

The compression is simply too high for the short duration cam in a heavy car with modest gearing. It would've worked OK in a Cobra or Mustang. If the heads are coming off I would first do an actual cc check - and then do some chamber relief work around the valve sides and the deeper side of the chamber wall to see if I could grow that volume a bit.

A cam change would help. The earlier Crane hydraulic rollers were pretty abrupt - short duration and high lift. Made for lots of cylinder pressure and torque - but very fussy on valvetrain and fuel sensitive. A cam with more duration might allow you to run more initial timing - total should still be no more than 36-38 - and in turn still feel decently strong without sacrificing lower end power. I agree that a cheap fix effort could be retarding the cam a couple degrees - but suspect it'd want more initial advance as a result and you'll end up in the same spot.

Barry Rabotnick

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  • Re: - Charlie on Jul 10, 2012, 4:43 AM