Compression

33IMP said
All I know is this:
I ran a 11 to 1 small block flat top zero deck on california pump 91, and it ran very well. Aluminum heads, good quench, and a 265 at .050 solid roller in a 2300 lb car meant I could get away with that.
I also ran a 10 1/2 to 1 440 with iron heads on california pump 91, but timing was critical. It has a 255 at .050 solid flat, weighs 3300, and is a LOT happier with a 2 to one mix of 91 and 100LL.

That’s a great demonstration of how weight affects the engine and how, as you said, timing is critical. I see a 1/2 point lower compression 10* in cam duration @.050 and an added 1,000lbs. is where the boarder line is approached in this particular case.

A case can be also made on the cylinder head chamber shape/design & quench.