Andy, you are right.
My understanding is that under conditions that marginally favor detonation, that detonation is more likely
at lower RPM. As RPM rises, even though you approach, and pass, the torque peak, the danger of detonation
goes down. This is likely due to increased mixture turbulence, and decreased time for bad flame front to propagate.
Is this correct or old wives' tale ?
If I was targeting 12:1, I would have no chance, but at 10:1 I thought it would be managable with enough cam duration.
The other guys evidently had good luck at 230-degrees; I guessed that the long rod deal would require more duration
to stay out of detonation, maybe 240~250 min ?
Sure you can put a big cam in it and kill off the low end torque but then you have a soggy bottom end that isn't any fun to drive on the street. If you are building a street car then cam it for the street and use premium fuel. If you can't afford premium fuel then lower the compression ratio to point that is safe to drive. A camshaft R&D project is really expensive and unless you have some decent test equipment you aren't going to know what is going on anyway. If you are planning on going EFI and have knock sensors on the engine then go for it. You can use the knock sensors to change the AFR or the timing. If you just have old school distributor and carb then how are you even going to know if you're on the ragged edge of detonation?
If you just have to build the combination that you're talking about then go ahead and build it but plan on starting off with higher octane fuel and then gradually trying different mixtures of fuel until you find out what it will run on. If it was my car I'd use a Sniper and a Hyperspark distributor so I at least had control over the AFR and timing. A knock sensor would also make
sense.
