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CAV-110 Drain Thread Engagement

Girraf

Well Known Member
Friend
Installing the drain valves in an RV-7 and the valve turns in very easily for the first 2 turns, then hits a wall where it gets really hard to turn. I experienced the same thing using the shrader valve attachment when pressure testing the tanks, and in that case, 2-3 turns was enough to seal the assembly. I used some boelube during pressure testing, and now using EZ turn for the drain valve installation. I'm concerned about damaging the threads on the Drain flange or driving the drain too deep into causing the flange to crack open.

How far in do these normally go?
 
Threads

If it is the standard 1/8x27 thread, it is a pipe thread so it is tapered. It definitely will get more difficult to thread the farther you go...
 
2 flats past finger tight, and make sure to use thread sealant -- Permetex #2 or Locktite 565.

If you don't like the depth, you can always cut the threads deeper with a 1/8-27 Pipe Thread Tap.
 
You can go a couple of turns past hand tight but be careful not to go any more because the soft brass can deform enough to cause the poppet to bind and stick open, that gets kind of exciting with fuel in the tank! I installed mine too tight and had to replace them both...
Bruce
RV-7A (purchased)
 
Drain valve installed with EZ turn lubricant. Finger tight was about 1 turn. Went an additional 1.5 turns with a 1/2" crescent wrench. Showing about 3 threads on the drain valve and I would guess about 3 engaged in the drain boss. Valve is actuating freely. Thanks for the inputs.
 

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Thanks for this. I have similar issue on mine and was wondering if my threads were stripped and I would have to retap.
 
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