Remember back in the days of the first GM HEIs?. They suggested gaps even as big as 0.060. Then they pulled back a little.

Here's the deal...The spark takes a LONG time to turn into a flame that burns across the chamber. The larger the spark when it starts out, the less time it takes. SO, if you could make a 0.250" spark, that would be super. It just takes a lot of voltage that'd rather leak out of the system somewhere else.

There's no doubt that any decent CD ignition will make a spark for a 0.060" gap in a regular street engine. It will show you any problems with the ignition wires and cross-fire or tracking in the distributor.

My 1993 Suburban with old faithful 5.7 chevy (350 TBI) had 100K+ miles on original wires, distributor cap and rotor. It was completely stock, I don't know if plugs had been changed once or not. I had logged every tank of fuel and knew really close what kind of mileage it'd get going 80 on the Interstate with a vacation load. So I pulled the plugs and found every single one had a very rounded center electrode and 0.060 - 0.062" gap. The wires were whatever chevy had installed when new, they kind of crackled as I removed them. I replaced with new BWD spiral wound wires, new AC plugs and new Accel distributor (original had burned out pickup coil and the ECM does the timing, so no change to the timing) Everything was new, the plugs were gapped to factory specs and we took our next trip. The mileage was exactly the same. There was no difference at all, at least to the tenth of an MPG.

From this experience I gathered that even with the crunchy stock wires and original cap and rotor, the stock HEI system had no problem firing a 0.060" gap, even with worn out plugs.

Your high performance system should be able to do at least as well.

R.