The main difference between low octane and high octane is that high octane resists exploding a few microseconds longer than low octane. That is basically all it does, give the flame a chance to burn it up before it can explode(detonate). Thats all it is. That was all well known 50+ years ago.
One of the things I've heard of is "expansion ratio" where once your piston has passed TDC on the compression stroke - the piston is dropping and the charge that's been lit. Any thoughts on this?
Great TTT 126 once anyone gets into this study they will learn so fast and answer just why they had an engine that didn’t perform as you design being down on power. I build a few of those myself. In the 60’s we would use a chassis Dyno in set base lines on a V8. Total timing and corrected carb jetting. Then we would use a modified distributor with locked solid advance. Using a locked advance distributor making pulls see if power would go up, down or stay the same at different rpm levels. Since we already had an advance curve in the original distributor. We would write down the rpm vs. advance in degrees. Having a map to work with made it hours instead of days to get answers. George thank again for presenting food for thought. Mike
Great stuff as always. Question I’m running a 124” with 11:1 cp pistons. Since I’m going in to replace a seeping gasket, I figured I would throw on the new SE extreme +1 heads. But notice they’re about 8 cc’s more volume than stock heads. I figured a little less compression is probably fine since my cam has a 30° intake close. It’s a loaded up bagger that I don’t run to redline. I notice currently on the PV on hills or when I get on it, it retards the timing a couple.
