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Old 10-16-2004, 02:15 PM
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max compression ratio on 89 octane

Ok, I've done a bunch of searching and haven't found a real answer to my question.

I want to put a bigger cam into my engine (ford 400m or whatever you want to call it) but the cam I want needs a higher compression ratio. Here's the cam specs:

Cam Style Hydraulic flat tappet
Basic Operating RPM Range 2,000-5,000 RPM
Intake Duration 050 inch Lift 216
Exhaust Duration 050 inch Lift 216
Advertised Intake Duration 272
Advertised Exhaust Duration 272
Intake Valve Lift with Factory Rocker Arm Ratio 0.524
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.524
Lobe Separation (degrees) 110

I don't want to buy 93 octane gas to cruis around town, so my question is, how high of a compression ratio can I run on 89 octane gas? Also, how high will my compression ratio be with said cam and flat top pistons installed in my motor rated at 8.5:1 CR stock?
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