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Allen or Univair fuel valve?

S

Supertwotwo

Registered User
I paid $40 for this on ebay, thought it was Univair valve, but my IA doing the annual says its Allen and not Univair and wont put it in my plane.

I thought the Univair and Allen valves were the same valve, I cant tell them apart, the first three attatched photos are the used valve I bought. The last photo is from Univairs website

Mine has the same F.T. and CURE print on it as the Univair, mine says F.T. OCT 89 and CURE 1Q89, what indicates its Univair?

I took it apart and cleaned it and put new Buna-N o-rings in it and it seems to work like new, looks new other than a few scratches, if someone is looking for one.
 

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They probably are identical. Problem is, Univair holds the PMA, not Allen. It is a little like patents and copyrights, but PMAs allow you to profit from your efforts forever.

Same for crankshaft seals - the seal for the small Continental is $20 from NAPA, but Continental seals it in a bag and quadruples the price. A mechanic caught using the cheaper part loses his license.
 
The seller said it was taken out of a PA-18, thought that was all info my IA would need. I payed $40. was free shipping so thats all I have into it plus four o-rings that cost $2.58 two MS29513-011 and two MS29513-114

Will put it back on ebay for $43. + shipping unless someone here wants it.
 
Super, does it have the provision for on, off, right, left, both? Or does it need to be modified? Sure need one now if still available.

Denny
 
flylowslow said:
Super, does it have the provision for on, off, right, left, both? Or does it need to be modified? Sure need one now if still available.

Denny
Click to expand...
I see no way to drill an Allen valve for a both position if it is not made that way. There is an o'ring groove machined into the taper of each fuel passage in the plug.
 
I agree with Steve, the Allen valves cannot be drilled out for 'both'.

I'm pretty sure my 1993 Cub has an 'Allen' valve without the 'both' position as OEM equipment. I would say if you have a Left/Right valve, its not available from Univair (as far as I can see) and you probably have the correct valve.

I also have a Cub Crafters and a Dakota 'Both' valve. I prefer the Dakota, because it has a built in stop and a nicer fuel selector lever. The Cub Crafters is an Allen valve like the one above, with three passages and the associated O rings. If this is what you are trying to install, I think the issue is more whose STC are you using for the 'Both' system.

I recall reading somewhere that these are not possible to service because of the lack of the non-standard O-rings?

Don
 
flylowslow said:
Super, does it have the provision for on, off, right, left, both? Or does it need to be modified? Sure need one now if still available.

Denny
Click to expand...

It was a two holer until an hour ago, I wouldn't have tried this if I had more than $40. in it, but I get an itch when someone says something can't be done, a little patience with a drill press and now she is a three holer. Not sure if I can sell it now but my old Bronco has a leaking fuel selector

Just have to be careful not to touch the outer rim of the o-ring seat when drilling the countersink, didn't want to leave any rough area around the new hole so countersunk it. No o-ring needed around the new hole, it's like the other two holes, should work fine
 

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Supertwotwo said:
It was a two holer until an hour ago, I wouldn't have tried this if I had more than $40. in it, but I get an itch when someone says something can't be done, a little patience with a drill press and now she is a three holer. Not sure if I can sell it now but my old Bronco has a leaking fuel selector

Just have to be careful not to touch the outer rim of the o-ring seat when drilling the countersink, didn't want to leave any rough area around the new hole so countersunk it. No o-ring needed around the new hole, it's like the other two holes, should work fine
Click to expand...

So how are you sealing the new hole? Been there, done that. Maybe you are smarter and more crafty than me.
 
Supertwotwo said:
It was a two holer until an hour ago, I wouldn't have tried this if I had more than $40. in it, but I get an itch when someone says something can't be done, a little patience with a drill press and now she is a three holer. Not sure if I can sell it now but my old Bronco has a leaking fuel selector

Just have to be careful not to touch the outer rim of the o-ring seat when drilling the countersink, didn't want to leave any rough area around the new hole so countersunk it. No o-ring needed around the new hole, it's like the other two holes, should work fine
Click to expand...

have turned many Univair ones into both position units.... was curious why that wasn't possible :)
 
Steve Pierce said:
So how are you sealing the new hole? Been there, done that. Maybe you are smarter and more crafty than me.
Click to expand...

The only hole that needs to be sealed is the one that isn't a hole, the one left that isn't drilled, and it has an o-ring around it and will seal tight. My new hole will seal actually not seal but neither did the original two holes, fuel gets around the inside valve body to those holes, but doesn't go anywhere because of the big o-rings and the little one around the only hole that is important to seal, the right tank when on left only, and left tank when on right tank only, and the outlet to the gascolator when in OFF position.
 
Mike, the o'ring seals the port from cross feeding between the body and the plug. Cutting the o'ring groove in the round plug was beyond my capabilities.
 
Supertwotwo said:
The only hole that needs to be sealed is the one that isn't a hole, the one left that isn't drilled, and it has an o-ring around it and will seal tight. My new hole will seal actually not seal but neither did the original two holes, fuel gets around the inside valve body to those holes, but doesn't go anywhere because of the big o-rings and the little one around the only hole that is important to seal, the right tank when on left only, and left tank when on right tank only.
Click to expand...

It will cross feed when it is positioned not to.
 
Supertwotwo said:
Gotcha, that could be a problem. Yes what I made was a simple both valve that will connect L an R tanks into one big tank, providing OFF/LEFT/BOTH/RIGHT
Click to expand...

I think you will leak between the two tanks when you try an isolate one. I don't have the valve in front of me but did the same thing you did several years ago and found out there is a reason the Both valve has o'rings on all the ports.
 
Steve Pierce said:
I think you will leak between the two tanks when you try an isolate one. I don't have the valve in front of me but did the same thing you did several years ago and found out there is a reason the Both valve has o'rings on all the ports.
Click to expand...

You could very well be right if the little o-ring is not doing it's job of sealing off the deselected tank. If that little guy is doing it's job than no fuel should get passed it. I do like this valve and would really like to see the inside of the Dakota Cub valve.
 
Supertwotwo said:
You could very well be right if the little o-ring is not doing it's job of sealing off the deselected tank. If that little guy is doing it's job than no fuel should get passed it. I do like this valve and would really like to see the inside of the Dakota Cub valve.
Click to expand...

The Dakota Cub valve is the same except on the back side there is a stop made into the valve body so you can only go to off in one direction. That is a Part 23 certification requirement. Cub Crafters has you install two bushings with AN3 bolts for the stops. Mark at Dakota told me that o'ring groove was somewhat of a challenge.
 
Take a close look at my valve, it does not have the little o-rings around each hole, only around the blocked ports. Do the new Univair and Allen valves come new with the little o-rings around the open ports?
 
I just put it back together, even with only the one o-ring it seems to be a tight seal around the closed port, possibly could have kept the other o-ring if I'd taken less off the countersink, but it looks like it will seal good as long as you maintain the o-rings
 
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Aerodon said:
I recall reading somewhere that these are not possible to service because of the lack of the non-standard O-rings?

Don
Click to expand...

They may or may not be, but the issue mentioned above by Steve of failing o-ring seals around the blocked non hole ports was reason for this service bulliten in 2002 www.extraaircraft.com/docs/service/SL300902.pdf

It lists the part numbers of the two o-rings, strangely though the larger o-rings that seal the valve from leaking outside are Buna rubber MS29513 and the smaller o-rings that seal the individual blocked ports internally in the valve those are Viton rubber M83248 not Buna like the larger o-rings. Viton rubber is known to shrink in colder temps, Buna rubber does not shrink in cold temps like Viton. That could be the reason for the failing seal of the small o-rings.

I used the Buna rubber MS29513 o-rings for both the small and large, will have to build another plane now to put the valve in and test it..
 
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You are correct. The valve I have apart has an o'ring on the two closed ports. So if I cross drill one port for Both, anyway I turn it the off tank is isolated with an o'ring. Now I have to figure out what I did years ago that it would not work.
:oops:​
 
Supertwotwo said:
They may or may not be, but the issue mentioned above by Steve of failing o-ring seals around the blocked non hole ports was reason for this service bulliten in 2002 www.extraaircraft.com/docs/service/SL300902.pdf

It lists the part numbers of the two o-rings, strangely though the larger o-rings that seal the valve from leaking outside are Buna rubber MS29513 and the smaller o-rings that seal the individual blocked ports internally in the valve those are Viton rubber M83248 not Buna like the larger o-rings. Viton rubber is known to shrink in colder temps, Buna rubber does not shrink in cold temps like Viton. That could be the reason for the failing seal of the small o-rings.

I used the Buna rubber MS29513 o-rings for both the small and large, will have to build another plane now to put the valve in and test it..
Click to expand...

I have replaced the o'rings, usually leak after they have sat without fuel for long periods of time. If you can put fuel to them and not have a mess they usually start sealing again. If you replace the o'rings wrap a rag around the shaft prior to pulling the plug out to avoid sending stainless steel balls and springs flying everywhere never to be found again.
 
Steve Pierce said:
You are correct. The valve I have apart has an o'ring on the two closed ports. So if I cross drill one port for Both, anyway I turn it the off tank is isolated with an o'ring. Now I have to figure out what I did years ago that it would not work.
:oops:​
Click to expand...


A possible theory that could have led to believing a drilled both hole would not work.

The drilled out both hole works with an o-ring sealing it, or without an o-ring sealing it. That might have tripped you up.

I have not seen a Dakota valve but by your description they make it work with the o-rings around all ports closed and the open ports. Allen doesn't use o-rings around its open ports which allows fuel to move freely inside the valve body, the Dakota sounds like a better design, but either way works as long as the closed non drilled port has an o-ring sealing it off the both position is going to work, although like you mentioned you will have the tanks cross connected in the Both position and the Off position, no way to stop that that I can see.
 
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My spring and balls were thickly coated with dialectic grease and the balls stuck to the ends of the springs, expected them to fly but no avail.. they stuck like glue to the spring which also stayed inside the valve. Going to grease it up good going back together.
 
When you go to change the o-rings on the Allen valve, do you pull the spool out the front (toward the shaft) or out the back opening (remove the snap-ring holding only a plate)?

George
 
The valve is in my hand, not installed. Still pull the shaft out or push the shaft thru?

George
 
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