Compression Ratios

[Bad70sbchevy]

So there's no generic rule of thumb for compression ratios to run on pump gas since it depends on dynamic compression, spark plug location, longest flame path, cylinder head material and design etc...

[pockets]

Originally Posted by Super73

you can have a 10-1 motor that requires race gas.. Again, it's not all about static compression ratio..

sure, but it is pretty rare, short of a supercharger, nitrous, etc.

[jrcaprai]

this might be easier... think of Cylinder pressure... you could have a 10:1 engine with a mild Cam 208/214° Deg @.50 and have a Cylinder pressure of approaching 200 psi, now you can have that same 10:1 compression ratio, and have a cam of 242/248° deg@.50... now that cylinder pressure is around 150 psi, due to the overlap bleeding the Cylinder pressure off... high cylinder pressures are the cause of Detonation, not Compression Ratio all by itself... also you can drop timing a few degrees and run an 11:1 engine on 91 octane, then when you go to the Track, bump up the timing and run Race Gas for full power.
My engine is a 11.6:1 408 sbc... Flat top pistons, 64cc chamber, zero deck block, and my cam is 242/248 @.50 and I run 91 octane on the street with 30° timing, because my cam bleeds off cylinder Pressure...
Reversion only happens at lower RPM's, once you get a above about 4000 RPM Reversion goes away because the air is moving too fast...