Hello all, After sitting for a few months I started my '46 and she's backfiring like crazy out of both tailpipes. New carb, 12 volt conversion, electronic ignition. Plugs are carboned up pretty good. Idles fine but pops and stalls on acceleration... Any guess what is going on here!
Did it run perfectly a few months ago? First thing I’d check would be the power valves. Did you have any backfiring through the carb?
I thought the same , ***uming that he has a ‘94 on it, but not a lot of information in original post. maybe something else to consider if it has been sitting a while, - is possibly something stuck open to have that much fuel going through it to carbon up the plugs and backfiring.
Really need more information. Does it backfire when it is idling? Have you done any testing? I would start with a compression test to make sure you don't have some type of valve problem. If that's good, I'd be looking closely at the ignition system. That's the most likely cause of backfires. If it only backfires when you try to accelerate, it could be a carburetion problem. Need a lot more information to point you in a direction.
Sticky exhaust valves. Gummy valve stems will slow the movement of the valves closing. Backfiring only out the exhaust is a good indication. If the ignition was working when it was parked it should not be a problem. Lean mixture on these is a cause of backfire, too, but normally out the carburetor. Does it have fresh gas in it? First thing I would try is to see if you can get it up on high idle and drizzle some Marvel Mystery oil or ATF down the carb until it smokes like crazy. We used to use ATF for such things and it would cure a number of things. Fresh gas, clean filters is a must after sitting a long time. Gas we get nowadays causes a lot of problems after sitting without a preservative added. Nasty stuff. Do a compression check first thing.
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