I had another mechanic look at it at the garage I work at. He said it was a misfire. It's a '68 with a 302, Edelbrock intake and carb, new plugs last year, wires, rebuilt stock distributor, good cylinder compression, timing is set to factory specs. I don't know where to look now. The engine shakes, and it pops and skips in the exhaust. I run 87 octane in the engine. Any ideas?