Hey everyone. I was thinking........ What would happen if you would weld a muffler in that was backwards? Heres the story..

I bought a Flowmaster 40 series a while back when i got sick of how quite my truck was, cut my original muffler off, then it all went to hell from there, well i welded a 40 series in there with no tail pipe. Well when i got the money together i had them cut both cats off, and weld in my existing 40 series. Well heres the problem. The sticker that was on it that said INLET was long gong by the time i handed the muffler over to be used.

Well what brought this up is today, i was washing my truck and i felt the exhaust tip and it was VERY hot, damn near burnt my hand. I know the exhuast system in my truck is not that long, but its bumped up to a 2 and a half inch pipe all in the stock location. I was just figuring that it would be cooler by the time it got to the tailpipe. Il get under it tonight and see if there is anything stamped on the muffler, but i think i remember looking and there wasnt anything stamped.. So am i pretty much a retard or could my muffler be welded in backwards and restricting. Its also not the sound i was hoping for.. But without headers its not bad.

Generally, exhaust systems get pretty damn hot. Hiiiiigh temperature combustion usually does that to metal..

Not saying that means that it might not be backwards, but if a shop did it you think they'd know the difference.

yea for sure they did an awesome job. But it was just weird to me lol

Backwards mufflers make exhaust come out your intake

95bronk said:

I know the exhuast system in my truck is not that long, but its bumped up to a 2 and a half inch pipe all in the stock location. I was just figuring that it would be cooler by the time it got to the tailpipe. Il get under it tonight and see if there is anything stamped on the muffler, but i think i remember looking and there wasnt anything stamped.. So am i pretty much a retard or could my muffler be welded in backwards and restricting. Its also not the sound i was hoping for.. But without headers its not bad.

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Even if it was in backwards, and even if backwards would cause restriction, I don't see what that would have to do with heat at the tail pipe.

If anything, do a back pressure test. If the test indicates that there is no back pressure problem, then leave it as is.

High exhaust gas temps is typically caused by retarded timing, AF ratio problems.

Smells like crap to, but i dont have any cats.. How di i do that backpressure test?

The easy way is with a vacuum gauge.

Hook up a vacuum gauge where the break booster is, run the motor with the trans in neutral/park and rev the motor to about 1500 rpm and hold it there. If the vacuum slowly drops down to a very low reading, then you have a back pressure issue. Why does it work this way? Simple. Vacuum is proportional to load, and restriction in the exhaust puts a load on the motor. As the load on the motor increases the vacuum in the plenum decreases. The longer the motor runs at the increased RPM the more the back pressure in the exhaust system builds up and that is what you are seeing as the reading on the vacuum gauge steadily drops.

Ok il have to do that one of these days. Thanks for the help man

95bronk said:

Smells like crap to, but i dont have any cats.. How di i do that backpressure test?

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My '93 has no cats and true dual glasspacks, no smell and I can run them in either direction as they're the fluted style...


With it being a flow master look at the case, you should be able to see the stitch welds holding the baffles inside, either they're pointed towards the front or they're pointed not towards the front.... Just a thought.