gas valve thread size

[Art Ebeling]

I want to connect the gas line up to my gas tank in my 11 but I do not have a shut off valve. I do have a reproduction shut off valve for at the carb that I got from Langs. What fitting and thread size is needed at the tank sediment bulb to connect to the gas line? Art

[DanTreace]

Correct repro part is the 2907 for your early sediment bulb.

Lang’s

[Art Ebeling]

Dan, They have been in backorder for sometime. I want to make a temp connection at the sediment bulb to fuel line. I will use a shut off at the carb. Art

[Scott_Conger]

Art

the sediment bowl thread is 1/4 NPT (to the valve that you cannot buy). As for the end with the gas line thread, it is an uncommon thread...I believe it is 1/2-18 if I am not mistaken (I am not in the shop right now to see for sure). I just had to help a fellow through this very thing on his Torpedo.

Tap/die for gas line thread are available easily on Amazon.

[DanTreace]

Scott, correct, the gas line nut and thread is 1/2" x 18.

[Scott_Conger]

Art

if you live near a hardware store, here's what I'd buy:

1/4 to 1/8 reducer in the sediment bowl
1/8 street elbow into the reducer and then pointed "down"
standard vendor 90 degree carb cutoff

this will clear the floorboards and give you a setup that your fuel line can attach to.

You will find that the reducer and street elbow must be installed to the sediment bowl and then the bowl screwed into the tank (the whole mess will not go through the hole).

Use Permatex #2 on all fittings and don't overtighten. It will seal tight and can all be removed if needed. Don't use Teflon tape on ANYTHING unless you really desire an unreliable car for some reason.

I am not near a town and had to make a reducer/adapter for my customer and used a standard shut off that I had in stock, like I described. Works fine.

[Altair]

Many times the jockeys in the hardware store don't much about these fittings and likewise in the auto parts stores too. There are 1/4 pipe taper threads and 1/4 pipe running threads and to the untrained eye they look the same. 1/4 pipe threads are 18 threads per inch, but will measure as 1/2 inch. The running threads are designed to seal when bottomed out. Some female threads are also tapered, a male running thread should not be put into a tapered female, it will go in part way and then bind up and leak.
There is also a system of tube fittings that go by the tube size and many are machine threads. A 3/16 tube fitting looks very close to 1/8 pipe however the tube fitting is a 3/8 fine machine thread. I have had countless discussions at the auto parts store over this issue and almost every time they ask me to come behind the counter and get the fittings myself. Fuel lines should not rely on a taper fit they should be a running thread fit and seal when bottomed out. With a taper fitting over tightening can crack the fitting. Gasoline will get through where water won't.

[Scott_Conger]

David

consider selling that valve to Art and let him be done with it!

BTW, you must be aware that sediment bowls and carbs have NPT (tapered) fittings, so am not sure how you're making connections without them.

Art

in any event, with the fittings I described (which are all NPT), you have a path forward to success until you can find the correct valve. Additionally, that set up will leave you with a fuel line the correct length to fit the correct valve when one surfaces for you.

[Altair]

I have an early brass fuel valve and the fitting into the tank is NPT however the fuel outlet is a running thread and seats by bottoming out against a flair. The original fitting on my 26 was a rubber hose with a moulded flair fitting. It was completely rotted out and I could not ever find the same fitting. I had to use a conglomerate of fittings to make it work and then the valve would leak and I had to fit in the line an accessory shutoff valve that required more bastardized fittings.

[Scott_Conger]

Yes, as I mentioned before, that is a 1/2-18 straight thread. It is the same thread as is on the unobtainable (for now) shut off that Art is looking for. It is not intended to be married up to a flared pipe. You've seen them that way, I've seen them that way, and they are all wrong. It is counterbored to accept 1/8 pipe with a felt packing and a PN 2910 packing nut.

to be clear: that outlet on the sediment bowl is not a flare fitting.

Flare fittings are intended (typically) high pressure, rigid applications of which this is not.

[StanHowe]

I believe it is sized for 1/4 tubing -- copper, steel or brass -- not 1/8 pipe, Scott.

Most of those fittings are 1/2 - 18; some - for some unknown reason - are 1/2 - 20.

[StanHowe]

Not necessarily these fittings, but many carburetor fitting threads are either 24 or 27 TPI. I have taps and dies in every size from #8-24 to 7/8 - 24 and every size from 1/4 - 27 to 3/4 - 27. There are also a lot of 32 TPI threads in carbs, most common is 1/4 - 32. I have every tap and die from 6 - 32 to 9/16 - 32. Most common use is 1/4 but there are others that use 32 TPI. There were a lot of old thread sizes that are no longer common. I have about half a dozen sets of Greenfield tap and die in sizes from 56 TPI in various sizes.

[Scott_Conger]

Thanks Stan

you're right. Not sure even why or how I typed that. Mis-stroke or brain fart...could be either these days.