pump gas engine vs. high compression

well see all we have is 91... so you need to give an idea what pump you are using...

but your question for a race only motor go with 12.5:1... then you dont need to o ring the block but still gives you a big boost in power over 10:1... bummer you will need to run 108 or so leaded,

BUT, with EFI and having the pistons,valves, and chambers coated you can still run pump gas by backing off the timing and staying out of the throttle...

for a street motor 10:1 is a good number... something also to remember is DCR, or dynamic compression ratio, which is what the comp is with the engine running... thats a better number to use...