Not sure why that '77 NYB should not run just fine on 87 or 89 pump octane fuel, with the 8.2 compression ratio and all. Chrysler's performance publications state that instead of trying to use higher compression and retard the spark to use existing fuels, it's better to run a lower compression ratio and normal spark advance, which they did.
I suspect that if you read the side of the bottle of the SNAP product, you'll see it has some sort of alcohol in it. Berrymans' used to have a similar small bottle of octane booster too. That small bottle's not going to affect the octane level of 20+ gallons of fuel very much, I suspect, but the alcohol might help some. If you were buying the normal octane boosters, that cost much more per treatment, it would not be cost effective to use them and lower grade fuel. I kind of suspect that whatever's in the SNAP or Berryman's smaller bottles has more to do with cleaning the combustion chambers and lowering the engine's octane requirements than really boosting the octane several numbers. But as long as it works for you, proceed. How's the fuel economy reacting?
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