I gave up trying to find an exhaust system that even vaguely resembles what I have on N891JF. I'm going to have to build another one that replicates it, unless I want to remove the engine, completely reconfigure the firewall and intake system, etc. Building a new system, as painful as that sounds, is easier than the alternative.

I was going to build it out of 321 stainless until I checked the prices. A 321 U-bend is $94, a 304 U-bend is $40, and a mild steel U-bend is $10. I need 8 U-bends (four are actually J-bends, but same price), just to think about getting started, we're talking $800, not to mention collector, tailpipe, flanges, etc, if built from 321 stainless. The existing one made it to 600 hours and was mild steel. I'll have N56ML back in the air before I put another 600 hours on this one!

By contrast, my Corvair system was almost reasonable built from 321, because it is built so simply using only three U-bends for six cylinders. But it's not a complex 6-into-1 system either, just a pair of simple 3-into-1 pipes.

I have everything I need to start on it, and that's what I'm doing all weekend, and probably next weekend as well. I built two mockup engines, one with the old exhaust to measure distances and angles from, and the other as the fixture to build the new system onto. We'll see how it goes.

One thing I learned along the way is that Great Plains has no exhaust systems built, but they do have fixtures, so they are "to order" with a 30 day lead time. The configurations are shown on their website at http://greatplainsas.com/scexhaust.html , none of which are similar to mine. Also, gauge size is not mentioned on their website, but they are 18g (.049"), rather than the 16g (.065")like the original exhaust system, so I had to get all materials elsewhere. I did buy flanges from them, but am not enamored with them as the mounting holes are huge compared to the 8mm studs, so I'll have to carefully center the flanges to the ports before I start welding tubes to them.

Mark Langford

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