I always thought that timing doesn't change once it's set? I mean, I've ran this engine for thousands of miles and it ran fantastic. I believe the cause of the hole was this: running too hot, which caused a leak in the intake manifold gasket, which made it run lean, which caused the hole (I actually could SEE the leak in the gasket).
and my 'rebuild' was: valve job and replace one piston. so no timing parts touched, and the distributor didn't leave the engine. so I don't believe the timing thing.
