Avcon fuel primer

[Dooley]

Do most Lycoming conversions have a primer. The paperwork I have does not mention one. I am in the process of re-installing a primer. I am plumbing it to #2 and#4 cylinders. Some people say stainless steel lines are required, at least firewall forward but I don't think so. I went to silver solder those little brass cones onto 1/8 copper and it was a very tight fit. Am I missing something something? Is 1/8 stainless tubing the same size? Can you even solder stainless?

[Bruce Fenstermacher]

Can't say you or I'd would be right using copper but that is what I'd use. Both my airplanes, a Cub and my 170, have copper but I don't have a Lycoming conversion in the 170. Don't see why having a Lycoming conversion would make any difference.

[blueldr]

All the tubing I am familiar with, whether copper, brass, steel, or stainless, has the same OD. I know that some stainless can be soldered, but there may be some that varieties that will not accept soldering.
I have always used copper for primer lines, However, I believe that stainless is required on fuel injection lines since they are under pressure when the engine is running.

[Dooley]

Yea my cub is copper also but it only goes to the intake spider. It's nowhere as hot as the cylinder area. I put this together looking at the aircraft spruce picture in the catalog. I had never seen these brass cones that mate up with the primer nozzles but it looked like no problem to solder them on. Probably few people have actually fabricated these things but I was surprised how tight they fit even after thoroughly dressing down the copper and heating the brass. Oh well I've done one and the other one won't take long after it warms up out there in the hangar. It's snowing here in Tejas. Thanks for the reply

[Green Bean]

We just rebuilt a a Lyc. 0-320B2A, (160HP) for our PA-18, and the primer is plumbed with copper to all 4 cylinders.

[Jr.CubBuilder]

The DelAir conversion which is pretty much the same as the AvCon uses stainless lines and they plumb into the cylinder, but I don't see why they couldn't be copper.

[Dooley]

Copper it is. Also is there no consenses on the number of cylinders. After having no primer for years I feel like half my cylinders primed will be a big improvement. Most airplanes have some kind of enrichment device for starting. I wonder why airplanes don't have chokes? My friend has a Varga with no primer.

[DaveF]

My Avcon uses copper primer lines inside the cabin and stainless lines FWF. I suspect the copper lines are factory original. I don't know offhand which cylinders are fed by the primer, but it's more than one.

[GAHorn]

Copper is fine for primer lines. Keep in mind that copper "work-hardens", which means that excessive bending/re-bending and vibration will cause it to become brittle and subject to breakage. If you must re-bend more than once you should anneal it.
Stainless is sometimes used in primer lines FWF to avoid vibration embrittlement, which is much less likely in a fixed installation area such as FW to panel.
The reason airplanes (and most inboard-boats) don't have chokes is because the ease of flooding with a choke creates such a fire hazard, and (for airplanes) the risk of vibration causing wear and loosening of choke parts which subsequently get sucked into the intakes is a hazard. (Airplanes with extensive sheet-metal induction systems should receive careful/frequent inspections of those induction systems. Many fuel-injection systems have this additional hazard. My Baron was a nightmare to keep maintained in that area due to a magnetic alternate-air door which suffered vibration and cracking.)

[Dooley]

Annealing does make a big difference. Stearmans use a lot
of copper lines but the service manual says they should be annealed annually. Maybe if you have cheap labor on the payroll with nothing to do but otherwise this is not realistic. I will use plenty of clamps to keep the vibration to a minimum. My Cub has had copper lines all it's life with no problems.

[hilltop170]

Stainless steel is not immune to cracking. This particular failure looks like it is in the heat-affected zone of the weld.

Stainless Steel fuel injection line

[Jr.CubBuilder]

Copper it is. Also is there no consenses on the number of cylinders. After having no primer for years I feel like half my cylinders primed will be a big improvement. Most airplanes have some kind of enrichment device for starting. I wonder why airplanes don't have chokes? My friend has a Varga with no primer.

Mine has three cylinders plumbed into the primer, I believe the manifold pressure gauge is using the fitting where the fourth would go. Which leads me to wonder why isn't the manifold gauge plugged an intake runner? It works though so I'm not going to loose to much sleep over it, and if I remember right only the left side of my C145 was primed but it's been a while since I saw it.
Chris

[bsdunek]

Stainless steel can be soldered using silver solder and the right flux http://www.machinistweb.com/forum/showthread.php?p=3366

I always figured priming an engine on one side was kind of like the cowboy with only one spur. If he could get one side of the horse to go, the other side would just come along naturelly.

[blueldr]

After I modified my engine to prime all six cylinders at the intake port, the engine started like a dream in cold weather.

[okflyer]

Is this the same Dooley we met on the USS Missouri tour in Pearl Harbour?