Two things are going to impact this dramatically. Do you have aluminium heads. If so they loose heat much faster than iron and typically resopond to about a point more compression than iron. My $.02 is around 9.5 on iron, and 10.5 on Alum. Two, what elevation are you at? I can run 86 octane no problem at 3000 feet but have to have 90 or higher at sea level. One more thing, Fuel injection will allow about .5 higher compression because all cylinders will be equally balanced. Carbs tend to lean out some cylinders relative to others and hence lower compression must be run so as not to detonate in the lean cylinders.
[This message has been edited by thunderbolt (edited 08-13-1999).]
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