We owned the engine rebuild shop during the late 80's through 2000ish. We saw the switch to unleaded. We cut heads for hard seats but damn near every burned valve was from an exhaust leak....not fuel choice.
High octane fuel is actually harder to ignite and can be a pita if you don't have the compression to run it and the carb dialed for it.
I'd run non ethanol and never look back.
