Posted for Don Skeele <dpske@wvi.com>:

I concur with Dan Schaffer's comments and will add, my 0-320 has the 8.5  high compression cylinders
with 650 hours and I had also modified the carb and engine inlets for air greater air flow.  I also run on the cool side for CHT's and oil temps, except for extra ordinary times running with the gear down or long holds on the ground.  Recent annual had compression on all four cylinders in the 75 - 76 psi range.   Hope this adds a bit to your quest..  Don Skeele  235/320  503-769-2563