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What Octane Level should I need for 10.5 to 1 Compression?

Ozzy, look for any of the Indian Casino's in your area. A friend of mine hauls fuel from Vegas that only goes to the Casino's. Its straight gas plus 10% ethanol. It does not contain any of the CARB additives that wreak havoc on our old cars. His company goes from San Diego county, his and my old stomping grounds, to the north end of the state hauling fuel to the Casino's.
The ethanol is what wreaks havoc on engines, tanks, pumos, etc.
 
A lot of variables here. First, a wedge and a hemi are two different animals when it comes to detonation resistance. Second, intake valve closing point (which varies greatly depending on camshaft design) will affect the dynamic compression ratio and that has a huge impact on what octane fuel the engine will tolerate. An engine can safely run 93 octane at 12:1 CR if the combination is designed to do so. Or it might detonate on 93 at 10:1 CR if the DCR is too high. At this point, you really need to know a lot more about that particular engine before you can make that fuel determination.

Agreed, would be nice to know more details of the engine.

Not that it's the end all but would be curious what a cranking compression test reveals.

Feel like most don't even know their true static CR even if they were the one that built it.
 
Agreed, would be nice to know more details of the engine.

Not that it's the end all but would be curious what a cranking compression test reveals.

Feel like most don't even know their true static CR even if they were the one that built it.
Especially critical in a hemi with a 170cc chamber.
 
I studied the dynamic and static ratios then pushed it to the max ratio that I could get away and still be able to fill up at the pump. Big block Mopar’s need lots of compression to really run hard.
 
Agreed, would be nice to know more details of the engine.

Not that it's the end all but would be curious what a cranking compression test reveals.

Feel like most don't even know their true static CR even if they were the one that built it.
Especially critical in a hemi with a 170cc chamber.
Agree. I have been lax on checking the last three engines I have put together. I have a pretty good idea, but I don't know, exactly. I have learned my lesson, and I have the tools to know exactly, (as I always did), next time I will know for sure.
 
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