exploding mufflers
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Joined: Jan 2008
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exploding mufflers
The muffler on my '77 F100 exploded immediately upon starting the truck after sitting overnight. It cranked as normal yet immediately "went off" hard enough to split the muffler wide open. There was no intermediate period of cranking and pumping the carb. It has been running rough for a couple of weeks with a few prior yet minor pops in the muffler. This one has a reman 302 with the stock 2 bbl and EGR plate still in place. Basically a fully stock truck with about 10 years service on this engine. Trying to trouble shoot this one before replacing and potentially blowing up another muffler. Would appreciate any thoughts on what might contribute to this issue. I pulled the carb and egr plate and found it coked up pretty good. The exhaust crossover where it enters the intake manifold was plugged. I cleaned it out and reassembled it but have not driven it much afterwards just yet. Thanks- Mark
Senior User
Joined: Apr 2005
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I would say that it is getting too much un-burnt fuel into the exhaust which caused your back fire. The same affect happens when you are driving a carburated car/truck with a manual trans. When you turn off the key and leave it in gear the motor still pullls in fuel and pushes it out the exhaust. When you turn the key back on the vehicle starts and you get a explosion or also called backfire.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
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From: Middle TN
They will do this sometimes when the ignition module (square box on fender) is starting to go bad. Buy one and try it. You should always keep a spare on hand anyway. A bad ignition switch can so the same thing.
Freshman User
Joined: Aug 2005
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You might make sure your exhaust isn't full of frozen water. I recently had this happen on a chevy truck, it cranked and i could hear compression coming out of the carb, thought i had a stuck exhaust valve. Then it fired and blew a big chunk of ice out the exhuast. If it was frozen enough I could see it blowing up a muffler.
Mike
Mike
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Joined: Jan 2008
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I'd have to agree that it sounds like a really nasty backfire. It's probably getting too much unburned fuel through the exhaust. That can be caused by a bad ignition module, or it could be a carburetor issue. I had a 73 with points ignition that would backfire and blow open the muffler while cruising down the highway. It scared the hell out of other drivers...and me. But someone offered me too much $$ for it before I ever got it fixed.
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Fleet Mechanic
Joined: Sep 2003
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From: savannah,ga
carb is running to rich or
it has an internal leak allowing fuel to bleed out
I would start with rebuilding the carb
it has an internal leak allowing fuel to bleed out
I would start with rebuilding the carb
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Joined: Sep 2005
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From: Saint Paul, MN
That happened to me a few years ago on my '79 Jeep CJ7. It had a 4 speed w/carb and a Ford dura-spark ignition (stock). I turned the key one day and instantly a loud bang and split the muffler. My neighbor on her deck next door said that she almost had a heart attack. Don't know the cause. I replaced the muffler and it never happened again.
