What is the horsepower gain if you increase the compression a half point. Going from 10.0 to 10.5 to one. Also can you get away with running 91 Oct on 10.5
Thanks

Not sure about the HP gain, bit I would neaver try to 91oct gas in a motor with 10.5 comp.

The gain depends on the engine hp you're starting with. Probably not more than about 25hp. Even 10:1 is too high for 91 octane.

yes you can even with iron heads, the key is the right amount of timing, you need to run the motor cool. you also HAVE to run a coolant cross over in the back of the motor on the INTAKE not the heads to relieve the steam pocket bbc have.

over all i think if you have 10-1 already your throwing away money, your going to feel no gain with a bump in compression at this point.

I think it's possible to run 10.5 with aluminum heads and 93 if you do everything right. I wouldn't even try it with iron. Backing off the ignition timing will kill as much hp as you get with the higher compression. Back it off too far and you start to heat up the exhaust valves.

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