Deceleration backfire
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Deceleration backfire
I searched but could not find enything. Pulling a load the other day i pulled the auto trans down into 2nd to help a little with the braking wile droping down in to a long canyon road. The higher the rpm got the more it would backfire out the tail pipe. I dont hear it at all when i dont have the extra weight pushing me . Any ideas?? OH yea this is what i am running 79' f-250 390ci holly truck avenger (670) c-6 auto ,headers nothing to crazy.
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From: the side of a mountain
its an exhaust leak some where, mine does it all the time. i cant keep doughnut gaskets in my manifolds for some reason and i know when they start going because it backfires out of the pipes.
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I dont know ,thats why im asking but i wouldnt think exhaust leek mabe the leek is coming from the backfire mabe its blowing out the doughnuts. I was thinking unburned gas is getting to the headers and lighting off . ??? timing ??? if so to much or not enough. then again you mite be rite but i built the exhaust my self and i think its pretty tight and only 3-4 months old.
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From: the side of a mountain
check the seal around the collector and the flange, have someone put a rag over the pipe and listen. whats happening is the leak is pulling in air and putting more oxygen into the exhaust gasses and mixing with unburnt fuel and it is igniteing. i know when i replace my doughnut gaskets it goes away but after a while when they start to deteriorate and leak the back fire comes back. i have had some pretty impressive flame shows going down hill and letting off the gas.
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From: the side of a mountain
it works like a vaccuum, that is why it is not good to run an engine on just heads, becuase it will suck more air in causeing a lean condition and burning valves its like adding oxygen to a fire. when you let off the gas the engine is still turning as fast as it was but it just isnt getting the fuel and air, with the ehxuast valve opening a little before you reach BDC it is going to pull some air in though the exhaust then it pushes out exhaust gas and some unburnt fuel and flame from the combustion and the added oxygen from the leak in there along with the unburnt fuel and the flame ignites and backfires out the pipe.
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