You need to optimize dynamic compression, valve timing events, and ignition timing for a certain octane level -plus a little margin for safety. Any fuel with octane rating exceeding what the build is designed for is just wasted money.
Octane and the burn curve aren't necessarily related. High compression engines need higher octane and also typically operate at higher RPM ranges, which requires a faster burn...
You'll find that fuels have varying Reid vapor pressures that will help with intake charge cooling more than others, which may help increase power via better atomization/distribution. A lot of stock eliminator guys will typically run C11 or C12, and those engines have less than 10:1 compression and huge cams that produce low cranking compression. Some fuels like hot vs cool engines (or hot intake charges from boost).
That being said, many people use race fuel for consistency in tuning run to run (or class rules) even if the engine doesn't require it. I have a big block iron headed engine here with 10.5:1 compression that doesn't care whether it's on pump or C12 (it actually picked up a tick on pump on the dyno). My stock 440-6 has some preferences that show up on the dyno in terms of fuel, but it's maybe 5 hp difference.
Pump gas is inconsistent but also oxygenated, which can help make power. You may also find that race fuel has lower specific gravity than the pump gas you're running, which means you need to jet up to get the same power input.
Overall - fuel testing and tuning takes a lot of time and effort. It's definitely not as simple as the guy at the cruise night spouting off "yeah she really runs good with the race gas!"
That'll run good on 87 prob, back in the day running my 440-6@9.8:1 with single 850DP I ran what we called 4 star leaded fuel, approx 97 octane, decided to add unleaded to it, and boy it sounded so much stronger, didn't go much faster but.
“If it were me”, and I were running an 8:1 motor in Stock, I’d initially be using whatever was the least expensive legal fuel on the list.
After the car was sorted out and quite repeatable......... then you could experiment with some different fuels to see if there is a performance gain over the cheaper stuff.
Of course, I wouldn’t be messing around in S/St either. Just put the 383 in the car, with the correct cam, heads, intake, carb and start making runs. Swap the short block when the new 400 is ready.
Octane and the burn curve aren't necessarily related. High compression engines need higher octane and also typically operate at higher RPM ranges, which requires a faster burn...
You'll find that fuels have varying Reid vapor pressures that will help with intake charge cooling more than others, which may help increase power via better atomization/distribution. A lot of stock eliminator guys will typically run C11 or C12, and those engines have less than 10:1 compression and huge cams that produce low cranking compression. Some fuels like hot vs cool engines (or hot intake charges from boost).
That being said, many people use race fuel for consistency in tuning run to run (or class rules) even if the engine doesn't require it. I have a big block iron headed engine here with 10.5:1 compression that doesn't care whether it's on pump or C12 (it actually picked up a tick on pump on the dyno). My stock 440-6 has some preferences that show up on the dyno in terms of fuel, but it's maybe 5 hp difference.
Pump gas is inconsistent but also oxygenated, which can help make power. You may also find that race fuel has lower specific gravity than the pump gas you're running, which means you need to jet up to get the same power input.
Overall - fuel testing and tuning takes a lot of time and effort. It's definitely not as simple as the guy at the cruise night spouting off "yeah she really runs good with the race gas!"
The last time my old M.W. race car ran in NHRA stock was in 1988, it ran better on VP C12 at that race than it had with the SO CA local race gas Daeco brand NHRA would check the polarity on gas in both SS and Stock but not in any of the Super heads-up classes back then Both of those classes can be tough to do well in good luck on your efforts