Snorkel

Today I installed a new oil return line on the #2 cylinder (front left).

The original line from Lycoming interfered with the snorkel, which is a know issue with the EXP119 engine. Conveniently, Aircraft Specialty make a drop in replacement line for just this problem.

I removed the original line, and test-fit the new one. It worked great, but I couldn’t quite get a flush fit between the flared tube end and the fluid fitting on the engine. After some fiddling around I guessed that the problem was the fitting clocking not being exactly right for the new hose. I removed the fluid fitting, cleaned the threads, and reinstalled it (Loctite 567). Once I had close to the right torque, I slowly rotated the fitting while testing the fit of the flared tube. It was easy to check the alignment by just feeling how much resistance I had on the b nut. Once it fit freely, I stopped rotating the fluid fitting and torqued everything up.

Clearance from the snorkel is perfect.

The gasket for the fuel controller arrived today, so I went ahead and installed the fuel controller and final torqued the nuts.

Following the engine maintenance manual, I torqued the nuts to 17 foot pounds (204. Inch pounds). The manual assumes there is no adapter, which there is, but this seems like the right value for the size studs that I’m installing onto.

With that done, I worked on the alternate air installation.

The alt air is a backup air intake for emergency use if the aim air intake were to become blocked (ice, bird strike, etc). There is a door on the side of the snorkel that can be opened with a control inside the cockpit. The standard Vans design doesn’t allow the alt air to be closed once it’s opened, so you’d have to take the cowl off to reset it if it were ever pulled. That’s ok, but it means you can’t test the mechanism as part of a run-up before takeoff.

Of course someone had solved this problem and come up with an alternative door design that can open and close using the cockpit control. The only difference is the door itself, it mounts onto the standard location without any modifications. This is what I’m going to install.

I needed to buy a hole saw because I didn’t have anything big enough. The plans called for a hole that is 2 11/16 inches in diameter. The closest diameter I could find at harbor freight was 2 5/8, and when I drilled the hole, it came out slightly over-sized, which was perfect.

Some of the instructions are a bit confusing, but carefully reading and following the steps made sense eventually.

The inlet is glued into position using epoxy.

Today I worked on fitting the snorkel, completing a few more steps.

With the fuel controller covered in plastic, I placed the snorkel on the flange, and then assessed the alignment at the air filter end, where it attaches to the baffling. The instructions warn that small changes at the fuel control unit can have a large impact on the alignment at the baffling. While true, I found that I needed to take a uniform amount off the fuel control end to get the other end to line up. In total, it was about 3/8 of an inch longer than it needed to be, and after carefully sanding it down, the alignment worked out well. I had to disconnect the oil return line to complete this step, and continually bend it out of the way to avoid interference with the snorkel. I’m hoping that the replacement line I ordered will clear the snorkel, because I’m proceeding with fitting the snorkel before I have the new line in-hand.

Once everything fit, I drilled alignment holes in the air filter end of the snorkel, clecoed them, then marked out the excess snorkel to trim. Then I could take the whole assembly off the airplane and trim the snorkel. I used a hack saw to cut about half an inch off the end of the snorkel, then carefully filed it down until it was flush with the shelf on the air filter holder.

I could then install it back on the airplane, and mix up some epoxy glue to seal the gap between the snorkel and the air filter holder.