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Old 01-15-2013, 07:37 AM
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Its going to be marginal at best. I recomend you use the best available pump gas in it.
Is it worth damaging the engine to save 10 minutes drive?
Critical on daily engine-water and engine inlet air temperature. Which will vary a lot under real world operating conditions. Like in traffic.
All you need is a hot day in traffic and the eninge is now breathing 180+F air. Now the engine is much more likely to Knock @WOT.
I recommend you tread softly on the spark advance setup until you have done enough street-real world testing
at WOT. And sneek up on the tune up. You may be fine one day and your luck may run out on the next day.
and it will knock at WOT. 10.94:1 is very very agressive for any pump gas, reguardless of advertized octane.

And the cam and its position in the motor will not change that much.
Cranking compression and theoretical DCR calcs have no bearing on the actual cylinder Pressure and Temperature or quality of the combustion mix in the cylinders when the engine is actually running at RPM @WOT.
As stated, CCing your heads is a good place to start.

The compression ratio-fuel octane you can get away with on a quick 10sec dyno test or a 10-12dec drag strip test on a cooled motor, breathing cool air under controlled conditons is a whole lot different the widely Different and much more severe
(HOTTER) engine operating conditons that you will experience while street driving. (the engine will get hot and or breath in HOT AIR at some point)
The real fuel octane requirement goes way up under these conditions. Which you cannot control or account for.

If that is the real engine compression ratio I bet sooner or latter the 91 octane gas will let you down under real world conditions. There is a big difference between 91 gas and 94 @WOT.

Last edited by F-BIRD'88; 01-15-2013 at 07:50 AM.
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