My ole 9N did the same thing, backfired so hard it blew the intake part of the gasket.... I replaced the gasket, still missed.... I then went to the Ford Dealer, and bought the tune up kit, that had the correct plugs, points, rotor and condensor. It has feeler gauges included in the kit to set the plug and point gap. It also has all the gaskets needed too. The problem is probably due to the condensor...I had the same problem with a Chevy truck one time, and I figured water in the fuel, or fuel breakdown, stopped at a garage and the mechanic there figured the same, (without my input) I put in drygas to burn the water out of the fuel, and it got worse. I finally looked at the points, changed them, no change. I then changed the condensor, and it purred like a kitten. Ran fine all the way from Michigan, to Southern Indiana where I live. Sure wouldn't have believed a condensor could cause a problem like that....but by using the elimination method, found it was the culprit. Hope this helps you... Art
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