I spent several hours at the airport this weekend, and pretty much finished the installation of the four pipe exhaust system.
The large heat muff mounted over the pipes from cylinders #1 and #3 added a lot of time to the installation. First, I had to loosen the #1 pipe at the cylinder so I could rotate it a bit, to get the tail pipes at the correct spacing the match the two holes in the heat muff. Then, I found that the outer shell of the heat muff was perhaps a bit smaller than ideal, so it took quite a bit of clamping pressure to get everything lined up properly. Even with all that I was unable to get the two screws that secure the two halves of the shell together to thread into their nut plates. I ended up leaving those two screws out - the two clamps around the whole thing will hold everything in place.
The hardware that connects the tail pipes together has mount points for supports that by design go pretty much straight up to the engine mount. But, the engine mount is fixed to the airframe, and the front end of the exhaust pipes move with the engine. It is far better to hang the tail pipes off the back of the oil sump, so all the supports move with the engine.On the right side, with the large two pipe heat muff, the heat muff outlet interfered with a straight shot from the exhaust system mounting point to the oil sump. I puzzled over this for quite a while, and eventually ended up fabricating a horizontal bar that connected the two mounting points together, and then extended to the right. This allowed the support on the right side to pass outboard of the heat muff outlet.
The second horizontal bar provided a convenient place to secure the fuel pump drain pipe and the sniffle valve drain. The breather tube was secured to the main horizontal bar which sits right on top of the two exhaust pipe supports.
I’ve got two things left to do:
- The MS21919WDG12 “Adel” clamp that secures the breather tube is quite close to the tail pipe from #4 cylinder. These clamps come in a number of different variants with different materials. The “DG” ones in my collection have Chloroprene cushions, rated to 212°F (100°C). I’ve ordered a MS21919WCJ12 clamp with a Fluorosilicone cushion, rated to 450°F (232°C). I hoped it would be in stock at Aircraft Spruce in Toronto, in which case I would have it on Tuesday. But, it has to come up from one of their US warehouses, so it’ll be delayed. I’ll fly with the current clamp, and replace it as soon as the new one arrives.
- When I started to mount the second heat muff, on the #1 cylinder pipe, I discovered that the end plates were cracked. I’ll fly with just the big dual pipe muff for now, and order new end plates for the second muff from Robins Wings.
I left the cowling off in the hope that the new Adel clamp would arrive on Tuesday, and I would install it before flying. But, given that it will be delayed, I’ll try to get flying sometime this week, assuming we get the forecast good, but cold, weather.