Hatz Biplane Association

Pretty quiet on the forum so here's a topic for discussion.

I recently purchased a used exhaust system off of an 0-290 powered Pitts. They are 2 into one, two separate stacks (right/left). They fit my 0-320 fine but will need a little tweaking/re welding to miss the engine mount. Not a problem since they are mild steel and not stainless with which I have 0 experience, and I weld with gas. The thing I'm curious about is the way these things are built. The mounting flange is welded to a piece of pipe about 2" long. That pipe slides into another pipe as a slip joint and is held in place with a vertical steel tab welded one to each pipe and then the tabs are bolted together. Seems like it would work, but I've just never seen a slip joint placed 2" from the mount flange. They are usually mid pipe. One old salt at my airport says he's seen this and never heard of one failing. My concern is that if one did fail, the breech would be only 2" downstream of the cylinder and would spew fire into my engine compartment. Not a pleasant thought. I like the fact that these pipes increase in diameter as the flow travels from cylinder to exhaust end. And they are relatively cheap and they will save me a lot of fabrication time.

So, any comments Hatz fans?

Kind of like this?


This is similar to how the exhaust attached on the C-170 (O-300) I once owned. The only real concern was ensuring a tight seal to prevent CO leaks. Other than that, no issues.

After much thought, I've decided to send it back and not use it. I noticed there was a lot of welding slag inside the tubes at the weld joints that can't be reached to smooth down. I suspect that would not be good with super hot gases blowing by at high velocities. I already have stainless flanges and some tubing. Just didn't want to have to spend the time fabricating it up. I've come across a old fellow who is a local classic and street rod builder who can fabricate my system using what I have.
Thanks for yoyr response Doug.