Exhaust huffing

EMD_DRIVER

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I've had an exhaust leak at the two flanges in my exhaust system, since I bought my 93. I didn't realize how bad it was, until I saw daylight through one of them when I was working on my transmission swap. I have a friend that owns a custom exhaust shop and he suggested that I cut the piece of the pipe with the flanges out and weld in a new piece. He measured and cut a piece of 2-1/2" pipe and flared the ends for me. The pipe cost me a whole $6!

I cut out the old piece and mig welded the new one in. WHen I started it up, I could then hear a huffing sound. The whole exhaust system (Except the flanges) was in pretty good shape, so I got to worrying that it was a valve problem, or maybe a bad injector.

While at work yesterday, I asked the guys to take a look at the truck. Their first observation was that the thing sounded great. They noticed no vibrations, that were indicative of a miss. Thinking that what I was hearing could be a valve, they had me get the thing good and warm. Then, they sampled the temp of the exhaust manifold at each cylinder. All eight cylinders were within 15 degrees of each other and all were around 250 degrees.

When we crawled under the truck, they said it sounded more like an exhaust leak somewhere. I'm going to put some welding gloves on and feel around the pipes, for leaks. I do know that I would MUCH rather patch/fix an exhaust leak, than to pull the heads!

I'm hoping that I was getting worried over nothing.
 

suv7734

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Can you hear the huffing coming out of the tailpipe at the back of the truck? That is the best place to get an indication of an exhaust valve issue since there's a lot of other noise and commotion going on up front. Check the exhaust pipes and also check carefully around the exhaust manifolds (cracks are not out of the question). Check the torque on the manifold bolts they can work loose.
Just some ideas.
 

EMD_DRIVER

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Can you hear the huffing coming out of the tailpipe at the back of the truck? That is the best place to get an indication of an exhaust valve issue since there's a lot of other noise and commotion going on up front. Check the exhaust pipes and also check carefully around the exhaust manifolds (cracks are not out of the question). Check the torque on the manifold bolts they can work loose.
Just some ideas.

I know about the manifold cracks.. My 87 has a badly cracked manifold on the driver's side. I'll be checking the pipes, as soon as I can...
 

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