What could cause my catalytic converter to overheat after a block or 2? It's not clogged, I'm told by a muffler man (there's plenty of exhaust air pressure coming out of the tail pipe). It vapor locks, too and won't start back up til it cools off- 30-40 minutes. The distributor cap's ok; new dist. rotor; new plugs; plug wires look fine; new fuel filter and gas cap. And it passed inspection yesterday! (And then left me stranded!) If the list of possibilities is too long, what kind of situation might be the prob? Not enough oxygen mixture?...If the original timing was off, could it cause this kind of thing?