Super six timing
This should be a sticky in all slant6 forums because it's such a problem with today's gas that people aren't informed of
There's nothing about today's gas that's inferior to yesterday's in terms of ignition timing. The relevant property of gasoline is its octane rating (resistance to spontaneous ignition/preignition/ping/"spark knock"). The octane ratings of today's gasoline are pretty much the same as they've been for many years, though the rating system changed from RON (higher numbers for any given fuel, "Regular" was 91 at sea level) to AKI (lower numbers for that same fuel, "Regular" is 87 at sea level). And today's gasoline burns a lot cleaner, which means
lower octane requirements in the long run on any engine, because there's much less buildup of knock-causing crud and carbon in the combustion chambers.
Yes, there were some very-high-octane Super High Test gasolines available back then (100-RON). The same is true now (94-AKI). No, nobody with more than two working brain cells was putting high-test gasoline in Slant-6 engines configured anywhere near stock back then, and the same holds true now. Yes, most of today's gasoline contains 10% ethanol. No, that doesn't have any effect on optimal ignition timing.
By all means spend as much time and effort as you can getting your advance curves optimized for your particular engine, car, location, fuel, and driving. Or pay DusterIdiot (over on slantsix.org) to do it for you. That's always been a good idea; the factory configuration is intended to work reasonably well for most drivers of most cars in most conditions on most fuel, within the bounds of whatever new-car emissions regulations applied to the vehicle any given distributor was intended for.
But it has nothing to do with today's fuel vs. yesterday's.
