Jon,
If the intake valve is only open on the intake stroke, and the plug were to fire later (delayed), wouldn't that mean that the intake valve would have been closed for a longer period of time. Advanced timing means "advanced before TDC"..if too advanced, you fire when the intake is still open. Later, or more delayed firing would be classified as less advanced, or almost ATDC.
Does this theory make sense, or did I misunderstand the post.
Stuart
