Before I sold my 1964 GTO, I had similiar problems with stock 3x2, and completely stock engine on 93 octane.
Tried a number of different jet combinations, no help.
Tried a number of different octane boosters, and after rebuilding the carbs because of the octane booster, still no help.
The fix: I started mixing race fuel and 87 octane regular. At a mix of 1 gallon race fuel to 4 gallons 87 octane there was no ping, even when the ambient here in "Misrey" hit 105 degrees F.
This was before ethanol came to our state. I suspect with the lower BTU content of the ethanol, the mix would need to be adjusted to a little more race fuel.
Jon.
__________________
"Good carburetion is fuelish hot air". 
"The most expensive carburetor is the wrong one given to you by your neighbor".
If you truly believe that "one size fits all" try walking a mile in your spouse's shoes!
Owner of The Carburetor Shop, LLC (of Missouri).
Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings.
|