I researched the gap issue heavily and came up with this same quagmire. Some say this, some say that. So I quizzed Jim Linder (my HEI guru) he said .045. I talked to Tom Langdon on the phone and he said .060. So rather than guessing, I ran actual tests to see exactly for myself which gap performs best with the 45k coil. Pertronix uses a similar coil, so the voltage isnt out of line.
At .035 fuel consumption was higher than .045. At .060 fuel consumption was higher than .045. .045 was the sweet spot. If you change the coil to a stock coil, then .040 was the sweet spot. Even the stock ignition tests came out better at .040. I am going with my test results. The tests were performed very carefully and all of the data is repeatable by anyone trying it themselves.
If you take the stock ignition, take the vehicle for a drive at .035. Record the gas mileage. Take the same drive gapped at .040 your gas mileage will be better and the engine will run better too. An older gentleman from Southern Cal told me so, and the tests proved it. Its exciting to take what people say, and test it. Then and only then do you truly know beyond a reasonable doubt. My testing was for HEI consumption however and not load tests. I still think they would track. Wish I had a working truck to test it! I have a 53 3100 that is close, but has no floor. There just isnt enough hours in the day.
My idle tests are the same idle you get in trucks, cars, boats, etc, so when fuel consumption is lower at idle, and the fuel mixture is stoic, seems to me the same results would track at speed all things being equal. One day I will be able to test under load.
