With the annual inspection coming due, it was a good time to address a nagging exhaust leak on my venerable ’88 F-Superduty rollback. The leak was between the exhaust headpipes and the catalytic converter. The threads on the bolts of the four bolt flange connecting the assembly had rusted completely away and the nuts were just roundish blobs. I knew that no wrench would be of any use, so I made use of the plasma cutter to cut away the hardware.
I soon discovered that the massive factory catalytic converter was completely gutted – either by a prior owner, or through hard use over several decades. The muffler wasn’t looking so hot, and the abandoned lines to a non-existent air pump were worthless.
I pondered for a couple mins, then ordered up some new parts and reached for the sawzall and set to work. Now was a good time to build a new exhaust system complete with dual cats, mufflers and pipes. The new system will shave some weight, fit more compactly under the truck, reduce hydrocarbon emissions, and improve power and fuel mileage.
After cutting off all the old, rusted junk…
I cleaned up the head-pipe flange and drilled out the holes to remove any remaining slag left over from the plasma cutter.
I used a piece of paper and a pencil to do a rubbing to transfer the dimension and bolt location to a piece of paper, and then transferred those a piece of 3/8 steel plate I cut to size with the plasma.
The head-pipes are 2.25 and I decided run 2.5 pipe for the rest of the system so I cut over-sized holes in the plate and then welded in two sections of pipe.
Generally, I would have preferred to use a 2.5″ hole saw in the drill press to cut nice neat circles, but I decided to just trace around the pipes with soap stone and then cut the holes free hand with the plasma. I used an old wheel to keep the work off the concrete. I have a nice welding table and vice that I should have used to be more professional but it was trapped on the other side of the shop because I took the truck apart before I thought about it.
Next, I tack welded on the converters and bolted the assembly to the flange to check the fit on the truck.
I’ll continue working my way back adding on additional pipe, dual mufflers and then the tailpipe sections, and finally welding on the hangers.