holy shit.very interesting.now,so is the proper way to see what fuel to run dependant on exhaust port height with xx? size domes.now since it says the higher the port,u will have lower compression with same domes as a motor with lower exhaust port,due to the larger charge,scavenging and crown temps.so how do u know what octane to run compared to exhaust port height?i know with my port on my 4 mill,the exhaust looked huge for a aggressive trail/dune port,i have standard base gasket and domes cut to 20cc.ive been running 93,and compression is around 140 psi.i havent had detonation issues,but wonder now the formula to figure octane to port height since compression ive learned isnt the way to accurately know.am i in the ballpark of figuring this out lol??mopar,i saw u replied as i was writing this.so uccr is that hooking up the gauge and kicking like how everybody checks?how do u find the volume number between the roof of the exhaust port and above (i believe u mean roof of the ex. port to the top of the dome?),and comparing that to whats above the piston at tdc (i believe this is the squish??).