800 series mufflers seem to have an outlet flange rot problem and my M813A1 is no exception. I purchased a used take-off muffler to replace the rotted one. However, I decided to try to repair the existing muffler while it was still attached to the NHC250 Cummins. If I failed, I had a backup muffler!
My exhaust stack was still bolted to the rusted out muffler flange. I removed the 4 bolts while the stack was still connected to the truck. I then removed the stack from the fender and cleaned out the leftover rust chunks.
A few years ago, I replaced my stock exhaust system on my Dodge Cummins and used a 4” exhaust kit. When I was finished, there were some leftover pieces, including the short adapter. I figured I could use the tapered part of the adapter to be the piece that fits into the exhaust flange and also allow another piece of 4” pipe to slide into it from the muffler. I had to slide a short piece of 4” pipe into the muffler outlet and then weld it into place. I had to have enough pipe sticking out to allow this adapter piece to connect with the exhaust flange. The reason being is that with the muffler installed on truck, you cannot easily weld around the back side of the exhaust flange. With the way I did it, it would be an internal weld between the exhaust flange with adapter pipe and the pipe I placed inside the muffler outlet. I prepped the exhaust flange and slid the flange down, measured for square and then welded it. I cut the pipe to length after welding to ensure a good fit. The pipe that slides into the muffler was cut lengthwise to allow it to fit inside the existing outlet hole (length was around 3"). I then welded it into place. The exhaust flange was then fitted to this pipe (back side of flange to muffler is around .375”, I hit .4”) and with some careful grinding; I set it in place and welded the two pieces together from the inside. You must be as close to square as possible for a good mating with the stack flange (if you are off, then you may have exhaust leak and we all know exhaust gases can kill because we read our manuals!). Once finished, I reinstalled the exhaust stack, placed exhaust gasket with some high temp gasket material (cut off excessive for looks once it dries) to ensure a good fit and then tightened it down. Now I have rigid stack again and a spare muffler!
Enjoy the pictures!
My exhaust stack was still bolted to the rusted out muffler flange. I removed the 4 bolts while the stack was still connected to the truck. I then removed the stack from the fender and cleaned out the leftover rust chunks.
A few years ago, I replaced my stock exhaust system on my Dodge Cummins and used a 4” exhaust kit. When I was finished, there were some leftover pieces, including the short adapter. I figured I could use the tapered part of the adapter to be the piece that fits into the exhaust flange and also allow another piece of 4” pipe to slide into it from the muffler. I had to slide a short piece of 4” pipe into the muffler outlet and then weld it into place. I had to have enough pipe sticking out to allow this adapter piece to connect with the exhaust flange. The reason being is that with the muffler installed on truck, you cannot easily weld around the back side of the exhaust flange. With the way I did it, it would be an internal weld between the exhaust flange with adapter pipe and the pipe I placed inside the muffler outlet. I prepped the exhaust flange and slid the flange down, measured for square and then welded it. I cut the pipe to length after welding to ensure a good fit. The pipe that slides into the muffler was cut lengthwise to allow it to fit inside the existing outlet hole (length was around 3"). I then welded it into place. The exhaust flange was then fitted to this pipe (back side of flange to muffler is around .375”, I hit .4”) and with some careful grinding; I set it in place and welded the two pieces together from the inside. You must be as close to square as possible for a good mating with the stack flange (if you are off, then you may have exhaust leak and we all know exhaust gases can kill because we read our manuals!). Once finished, I reinstalled the exhaust stack, placed exhaust gasket with some high temp gasket material (cut off excessive for looks once it dries) to ensure a good fit and then tightened it down. Now I have rigid stack again and a spare muffler!
Enjoy the pictures!
