Figured out why the Autolite plugs I pulled out of my 302 before taking it in for a rebuild no longer threaded into the heads. The machinist determined that the heads of my 302 from an '83 E-150 were marginal at best. Turns out he had a set that came of a FI 302 that the customer wanted aluminum heads installed. So he did a valve job and surfaced them and installed them on my 302 block. But it turns out the old plugs wouldn't thread into the new heads. Both heads had 14mm spark plug threads. After some research he determined it needed Autolite 2545 (or equivalent) plugs. The reach is different from the old Autolites that were in the 302 when it went in for the machine work. This solved the problem BUT my question is what plug gap to set the new plugs at. My 302 has a point distributor and 2 barrel Holley. Prior to the head change I set the gap at .035. The recommended gap is between .044 and .054 depending what chart you look at. I'm thinking that I should go with .035 but any insight is greatly appreciated. Thanks in advance.
The bigger gaps work well with the later electronic ignition, but for an old point setup, use .035 and be happy
I would gap them as required for the ignition system you have, too much gap can over stress the coil. If it were me I would do them at .035 just as before.
Thanks @squirrel and @Pocket Nick. I thought .035 was the correct setting but confirmation from you guys definitely settles it.
I've never noticed any appreciable improvement in mileage, performance, throttle response, etc. from setting the gap any wider than .035 regardless of the ignition system. I still set them at .035 with HEI.
HEI was designed to burn lean mixtures, and the wider gap helped it do so. With the carbs most hot rods run, it's not necessary.
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