I finally did some testing today,8.8 to 1 360 with stock Edelbrock heads and a hydraulic cam. I tested all 3 grades of fuel from a local station that had the best 93 octane premium when I tested several a couple of years ago.
87 octane was the worst,110 VP wasn't far behind .
The 93 made less power than the mid grade,which I believe is 89 octane R/M2 I forgot to check that.
Overall best was the midgrade . I tested each for best power A/F and timing .
I will print some sheets out later,but the average difference between the premium and 110 after tuning was only around5 hp. Low speed torque was where a lot of difference was noticed .
Keith