Thread: gas and valve questions 327/ 350 HP

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93 oct or higher. Additives are across the board pretty equal. Cleaning agents are the biggest difference in these products.There will be a political storm now that I've stated that. Don't pull back on fuel ratios Carburation specs) to save gas. It creates havoc with pre detonation and unstable combustion. If you wish to get a jug of av gas or race fuel mix it in to your gas with small amounts. Maybe 5:1 ratio (5 gas :1 race). You mind it is a bit much to start but as you play you'll find your solution.

I ran a 400 hp 350 on the street in the 80's with 11.5:1 CR. Ran unleaded premium. At first it pinged a little, then I indexed the spark plugs so that the gap pointed up between or towards the intake valve, and the pinging stopped completely. I ran a Mallory Unilite back then with a 40 kV coil; point being you'll want a good spark ignition IMO.

An alternative to race gas is a water injector. I did the race gas bit with my 68 427 Vette running 11.7:1 CR. IMO this would be less of a PITA.

You might consider some aftermarket aluminum heads as well.

Regards, Kitz