[jlhansen]

The carbon deposition would appear to me to be a problem. With the engine mods I did in the '60s and '70s, any defect in smoothness of the combustion chamber would add chances for detonation and dieseling.

That being said, however, these new emission-controlled engines behave completely differently from the old ones. I'm amazed at the things designers do now without causing problems. I keep coming back to the point that there seems to be a delicate balance between components and their interactions. I would wonder what part of the combustion formula would go wacky with a mod like that.