I'm probably famous for wanting to make every little part of my KR2S, and have even gone to the trouble of buying a TIG welder and learning how to use it so I can make some of the steel and aluminum components in my airplane. But I'm really getting antsy to fly soon, and welding up a complete exhaust system would take me forever so...

...I talked Terry Bailey into buiding one for me. This system is his design, and is totally stainless steel throughout. Tubing is .065 wall, so it'll be here long after I'm gone.

The flange mechanism is Terry's design too, and used some sort of spigots that he machines to match the angle of the exhaust flange donuts. After looking at it, I may cut off the outer half of the circle and save a little weight, which will leave them looking something like a distributor hold down clamp. The complete exhaust system (all the way down below and a foot past the bottom of the cowling) weighs right at 9 pounds, which isn't too bad when you consider that GPASC's 4 cylinder exhaust system weights 7.8 pounds, and I've got two more cylinders.

The welding on these headers is unbelievable, and he went to the trouble to do it right by purging the insides with argon for perfect weld penetration and no oxidation on the other side. Although I probably could have built a set of these, it would have taken me at least four months, and I couldn't have gotten anywhere near the quality. These things bolted right up, look immaculate, and best of all, I was working on my plane while he was building them! This was a lot of work for him, and I really appreciate the effort. He might be talked into making another set or two for other VairHeads, if you throw about $500 bucks at him. The flange allows the downpipe to take on whatever shape is needed to fit different airplanes. He's at baileyt@alltel.net.

Before flying, I installed an air/fuel mixture gauge. This page shows the oxygen sensor "bung" and gives part numbers and source for gauge and sensor. Now that I've been flying, I can tell you this thing is invaluable! Several times I'd have gone down had I not known exactly which way to move the mixture knob to straighten out the engine...

At 440 hours, the exhaust system cracked at one of the welds. I rewelded it, and now we'll keep a closer eye on it!

Here are some inserts that I installed in 2007, which reduced noise levels considerably, by about 4 db.

Update, July 2007

I now have 470 hours on the system described above. It had problems, mostly that the connection to the exhaust stubs was less than reliable. As you can see, the clamps were poorly designed and would bend rather than clamp, and often cocked the exhaust to one side or the other, compromising the seal.

Another problem is the fairly useless flanged connection from header to "tailpipe". Terry Bailey did this to allow him to make one set of headers to fit many applications (such as the Dragonfly) by merely switching tailpipes. To me though it's been a problem keeping gaskets in there, as the picture above shows, as well as dead weight. This is what it looked like when I landed at William's house, and the safety wired firesleeve is a stop gap measure to get me back home without melting my oil line. This picture is a pretty good argument for firesleeving everything near an exhaust system. A stainless shield was also added between the flange and the oil cooler, because I didn't have a spare gasket with me.

Another disadvantage with my old exhaust system (shown above before it was ever flown) is that it extends so far back that it comes very close to firewall, preventing me from mounting a larger oil cooler or other stuff that would be nice to have room for. Any new design would need to head downwards from the front cylinder at about a 22 degree angle so it conveniently exits right at the bottom of the firewall.

William's been making his 601 exhaust systems from these stub pipes which he has CNC'd. They are a sweet fit to the stock Corvair stub pipes, and make a very tight seal. I bolted three of these up to my engine and went to work cutting tubes to fit up to them. William then used his exhaust system jig (which locates the three stubs exactly with relation to each other) to weld all the pieces together into an exhaust system that fits perfectly.

This exhaust system weighs half of my previous one (4.5 pounds total for both sides), without the extra flanged connection (or possibility of leaking), and opening up some space on the firewall for other things. The two large threaded bosses are from Summit Racing for my O2 sensors, and the six smaller ones I made myself for the EGT sensors.

After welding on the sensor bosses, I decided I'd ceramic coat the headers for longevity and to lower heat transfer through the headers into the area under the cowling. This is supposed to increase engine power slightly also, by rejecting the heat faster. The coating is Turbo-X from Techline Coatings, part number 18008, and I only used about a quarter of the 8 ounce can do both outside and inside (as best I could). I bought the "mini detail spray gun" on sale at Harbor Freight (part number 92126), and it's a really nice little touch-up gun. I did have to sift through three of them to find one that had adjustments that actually had full travel though. It has a nice little spray pattern and is very easy to cleanup after spraying, and it doesn't take much air pressure to run it.

These flanges really are a perfect fit. I suspect this will be the end of exhaust leaks for N56ML.

Here's the final result, although there was still some tidying up to do with EGT probe wires and that sort of thing. I should have masked off the areas where the carb heat and cabin heat muffs go, but I wasn't entirely sure where they needed to be, and I wanted to see how much of a difference it would make anyway. The coating should be easy enough to remove mechanicallly, by sand blasting or wirebrush. I'll update this later when I have more info on that. From a performance standpoint, it may put out slightly more power, but it is definitely smoother. That may be a function of having two oxygen sensors in it, so that each downtube has the same amount of restriction.

Return to Mark Langford's KR2S Corvair engine project.