Round 2 on the measurements. Outlet: Extends 9 1/2" inside the body, through the baffle plate. The end past the baffle is plugged and has (28) 7/32" holes randomly drilled in it between the end and the baffle. 2 1/2" from the baffle towards the outlet, it has another plug. There are (34) 7/32" holes randomly drilled between the baffle and the plug. It has (22) more 7/32" holes randomly drilled between the plug and the outlet end plate. I have no information on the outlet pipe past the end plate, mine has rotted off and is missing. If anybody has that information to share, it would be appreciated. On the inlet side: The pipe extends in to about 5/16" from the baffle and is plugged at the end. There is a hole in the baffle the size of the pipe for exhaust flow. The inlet pipe has (45) 7/32" holes randomly drilled in it. The "pipes" inside the body appear to just be sheet metal formed to be a cylinder and the seams are not welded. Also the 1 3/8" pipe from the engine is a separate piece slipped inside the internal pipe and is welded in place. I found a piece of 1 1/2" O.D. stainless tubing that seems like a good size to build the internal pipes from. Matches the O.D. of existing well. With no open seam to pass exhaust through, more holes may be needed to increase efficiency. The holes drilled in the internal pipes look like they hired Jr. high school kids to make these for them.