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Old 11-22-2007, 03:05 PM
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There is no magic formula to come up with an absolute compression ratio limit for a fuels rated octane.
The rated octane of a fuel is a broad number based on the average of two different lab tests on a specially build motor under two different lab test conditions. The octane rating is a average of the two tests.
Every fuel acts a little different. Every engine is a little different.

All engines will make more torque with a high(er) compression ratio.
If you want to build for the street keep the compression ratio within what will work with street pump gas.
A street tunnel ram will work very well with 9.5 to 10:1 compression and 92-94 octane pump gas.
Just don't get carried away with the camshaft duration. Pick a cam that makes good power from 3000 to 6500rpm.
Use a 3500+ stall converter for an automatic. Use a good bit of rear gear ratio.
4.10 or more is good. 2.73 is not going to cut it.
Keep the carb cfm size reasonable. 900-1000 combined cfm is plenty for a street small block.

Don't try to crutch fix a motor with a excessive compression ratio by overcamming it. That won't fix it, or make it run on a certain fuel.
You'll just end up with a motor that is a dog.

Last edited by F-BIRD'88; 11-22-2007 at 03:15 PM.
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