[njsteve]

Do you have the plug wires installed wrong? I once accidentally swapped #5 and #7 on the distributor on a small block Chevy. Because they were so close in the firing order, (1-8-4-3-6-5-7-2) there wasn't much of a noticeable misfire in the engine, but one header pipe (they were painted white at the time) glowed green from the extreme heat.

Or is one side of the exhaust blocked? Internally blown muffler bocking output?