Technically, the Velocity is a “kit”. Which means that I should get a bunch of parts and then assemble them into an airplane. With a “plans built” plane, all you get is a bunch of paper. From which you build (or acquire) every single component. Even though the Velocity is a kit, that doesn’t mean there aren’t some of the same challenges that “plans built” folks have.

On the Continental IO-550 engines, each of the six cylinders has a drain. This allows excess (unburned) fuel to drain out of the cylinder at engine shutdown or if the engine is over-primed prior to start. These six drains have to be merged into a single line which then goes through a “sniffle valve” (I kid you not) that allows fuel to exit but does not allow air to enter. After the sniffle valve the line exits the bottom of the fuselage.

Here’s the section of the manual that describes this part of the build:
The intake manifold on the Continental has 3 separate 1/4” lines on each side of the engine coming from each cylinder heads to a manifold. From here we need to make two hard lines that join together at the back of the engine at an AN824-4D Tee fitting. After a short run from the AN824 you will switch to Mil-H-6000 line. Before the drain exits the cowling you have to connect to a short run of 1/4” aluminum line that is
flared at one end with an AN818-6D and an AN819-6D. Screw in an AN815-4-4D fitting into your 1H19-6 Cylinder drain valve. This is provided by Continental. Attach you line to this and route the drain valve out the bottom of the airplane.

Okay, pretty straight forward. First, I need this drain valve. I looked on and off for almost 6 months. I got a number of different part numbers but still couldn’t locate one. Finally, I got a lead at Global Air Parts and was able to pick one up.

Now I just need to run the two lines from each manifold to the tee. Except that I DON’T HAVE A MANIFOLD. Nor do I have the lines coming out of each cylinder going to this “manifold”. At the bottom of each cylinder I have a fitting. And that’s it.

I asked my A&P to call me the next time he had a Cirrus (or any other plane with an IO-550 engine) in the shop so I could take some pictures. Within a couple of months, I got a call that a Cirrus was in the shop so I headed out with my camera.

Here’s a picture of the three cylinder drain lines meeting at the manifold with a 1/4″ flare fitting.

Well, I can’t make THAT. So now I start looking for a pair of these things. But are they engine parts or airframe parts. Everyone I spoke to said “Airframe Parts”. Which mean they are available from Cessna, Cirrus, Piper, Beech, etc. This typically means insanely expensive. For example, the sniffle valve cost me $265.00 (used).  So I check with all the used parts sources and I can’t find anything. When I went to Oshkosh this year, I looked at every single IO-550 that I could find. Most had the drain lines like the Cirrus. But a couple had homebuilt lines.

So I made the decision to fabricate my own. I went over to the AeroMart where all the vendors sell everything that you can think of and picked up a bunch of AN fittings.

When I got back home I decided to run the idea past my A&P, Lynn of Motive Services, to see what he thought. Lynn is my go to guy when I have a question about acceptable practices, best methods, is it legal, etc. He did some digging and discovered that the “Tube assembly, Cylinder drain” is actually a Continental part (PN 643584). With a price of about $200 each. Since this is a drain line, not under pressure and will only see fuel if the engine is over primed or after it’s shut down, I decided that fabricating it was acceptable.

So I got the tubing bender, flaring tool, compression fittings and got to work.

Here’s the tube from the #6 cylinder.

Here are the odd cylinder drains run into a 4-way AN fitting

Now I need to run a line to the front of the engine to meet up with the even cylinders drain line. The bending on these lines was a little tricky because there were a number of directional changes. This is the stuff that Malcolm excels at.

Odd cylinders drain line running forward.

At the front of the engine, I had to drop the line a bit to clear some components of the engine. So I had to make a standoff for the Adel clamp.

Then the lines from both sides meet at a “T” fitting.

From the “T”, I made up a braided steel hose that would go to the firewall. The manual says that unshielded rubber hose is okay, but I like using the braided line. Since it’s not in use during engine operation, I don’t think firesleeve is necessary (I’ll check with Lynn to be sure).

Looking up from the bottom at the front of the engine.

I mounted the sniffle valve on the firewall and attached the other end of the braided steel line to it. I’m thinking about putting a 90 degree fitting on this end so the hose has better routing (I’ll put another clamp on the line later once I’ve changed the fitting).

And finally, I ran a short length of 1/4 aluminum line from the sniffle valve out the bottom of the fuselage.