GAV thread sealant
 

Hi folks - looking for recommendations on sealing the GAV threads. Previous owner bottomed it out, and then used some type of pipe dope.

Tried Teflon tape, but it still weeps.

Searched the threads and found a recommendation for Permatex Aviation #3.

Is there something better someone has used? All my thread sealants do not work with gasoline :(

Thanks,

Scott

Re: GAV thread sealant
 

I do have Loctite 660, which is impervious to gasoline. More of a glue than a sealant.....

Re: GAV thread sealant
 

Do not use teflon tape. It will find ways to plug jet orfices.

Re: GAV thread sealant
 

I was worried about that - tried to keep it to the upper threads. Keep my fingers crossed it stayed where I put it.

Re: GAV thread sealant
 

There are fuel proof Teflon tapes available. I've used them for years with no problem. They are generally yellow here and the white ones are for use in non fuel related areas like water pipe joints.

Re: GAV thread sealant
 

I think yellow Teflon is for GAS, not gasoline. White Teflon works well for water plumbing projects.

Re: GAV thread sealant
 

https://en.wikipedia.org/wiki/Thread_seal_tape

There are two US standards for determining the quality of any PTFE tape. MIL-T-27730A (an obsolete military specification still commonly used in industry in the US) requires a minimum thickness of 3.5 mils and a minimum PTFE purity of 99%.[4] The second standard, A-A-58092,[5] is a commercial grade which maintains the thickness requirement of MIL-T-27730A and adds a minimum density of 1.2 g/cm3.[5] Relevant standards may vary between industries; tape for gas fittings (to UK gas regulations) is required to be thicker than that for water. Although PTFE itself is suitable for use with high-pressure oxygen, the grade of tape must also be known to be free from grease.

Thread seal tape used in plumbing applications is most commonly white, but it is also available in various colors. It is often used to correspond to color coded pipelines (US, Canada, Australia and New Zealand: yellow for natural gas, green for oxygen, etc.). These color-codes for thread sealing tape were introduced by Bill Bentley of Unasco Pty Ltd in the 1970s. In the UK, tape is used from coloured reels, e.g. yellow reels for gas, green for potable water.
White – used on NPT threads up to 3/8 inch
Yellow – used on NPT threads 1/2 inch to 2 inch, often labeled "gas tape"
Pink – used on NPT threads 1/2 inch to 2 inch, safe for propane and other hydrocarbon fuels
Green – oil-free PTFE used on oxygen lines and some specific medical gasses
Gray – contains nickel, anti-seizing, anti-gailling and anti-corrosion, used for stainless pipes
Copper – contains copper granules and is certified as a thread lubricant but not a sealer

In Europe the BSI standard BS-7786:2006 specifies various grades and quality standards of PTFE thread sealing tape. [6]

Re: GAV thread sealant
 

Here is a gasoline resistant teflon type sealant.

http://www.gasoila.com/products/pipe...d-sealant.html

Re: GAV thread sealant
 

Do NOT use teflon tape. It does not matter if it is gasoline resistant. Teflon tape shreds in the threads, then little pieces travel along the pipe until they can't go any further. Like when it gets stuck in a jet.

Re: GAV thread sealant
 

Permatex makes a dedicated Thread Sealant, works on my carbs. But#2 Permatex will seal about anything needed on a model A. I agree with the don't use tape folks.

Re: GAV thread sealant
 

Agree with Vince and above from SR. Permatex #2 is good and is the sealant of choice
Larry

Re: GAV thread sealant
 

The thread for the gav is 1/8-27 NPT. If someone has chased this thread with a different tap size (straight thread) this could be your leaking problem. If this is the case you might try an old plumbers remedy. Remove a fine strand of cotton from a piece of cotton string. It should be cotton not synthetic type string. Wrap the thread with the string using a couple of passes and apply paint for diesel & gas fuels to thread. The theory behind this is when the fuel contacts the string it will expand or swell and prevent leaking.

Re: GAV thread sealant
 

Thanks for all the feedback. Got it loud and clear on the teflon tape!

Found the Gasoila last night on Amazon so that should be here in a couple days.

I do not think someone tapped it wrong, I think they simply cranked it all the way in hoping it would seal and then used pipe dope on it. I did not notice at first the threads are below fuel level so never gave it much thought!

I will report back how the Gasoila works.

Re: GAV thread sealant
 

I had a small leak at the GAV (replaced the needle and use Permatex 2 did the job... just a little on the threads only.

Re: GAV thread sealant
 

Make sure you don't have a hairline crack in the carb
Have seen that happen from them being torqued in

Re: GAV thread sealant
 

Had this problem also. Had a hard time trying to find this but finally did. So check over the carb for this.

I think I got this when I screwed the outer screw thing in to tight.

Re: GAV thread sealant
 

Checked closely - did not find a crack.

Tried the gasoila sealant, allowed to dry for 24 hours +, leaked :(

Ordered Permatex Aviation #2 - now all back together and letting her cure overnight. Fingers crossed!

Re: GAV thread sealant
 

Permatex makes a sealer called Anaerobic gasket sealer. It is a red gel like sealer. Apply a SMALL amount to the threads with a Q-tip, insert the GAV housing, and when it dries it seals completely. A bit pricey, but we use it on a lot of things. Very good!!

Re: GAV thread sealant
 

As Mitch indicated you could still have a crack... I might suggest bench testing the carb as well for leaks. It's important to get the same "level" as it would be on the car... but you can lightly mount it in the bench vise, use a shortened fuel line going upward with a small funnel, and fill the bowl with fuel... as it would on the car the bowl will fill, float valve close and hopefully sealing well, and the carb should be dry. You can let it sit for some time and even overnight. If it is dry you should be good, if not then you have to determine where the leakage is. If it's coming out of the throat then the cab or main jet not tight in the seat or you more likely have either an incorrectly set float or needle and seat leaking, which is causing it to top over the jets.

If it's leaking externally at the gav area look at the plugged area at the bottom of the GAV, maybe it's weaping or you have a crack. I've had a carb or two have some issues in this area.

Good luck... confident you will find it!
Larry

Re: GAV thread sealant
 

So far I am looking good. Used Permatex 80019 which is simply labeled as Aviation. Not sure what number follows, different websites refer to it as #2 or #3........

Applied last night after cleaning everything up.

Turned the gas on this morning (carb had been dry overnight). Let her sit 2 hours with no leaking. Will give it a longer test later today.

Hoping to take her to Druyea Days in Boyertown if I can break free tomorrow.

Re: GAV thread sealant
 

EXCELLENT idea, Larry! I will be using your method this afternoon.
Thank you!

Re: GAV thread sealant
 

Missed Druyea Days, but went to a local show - all is well. Been out a couple times and no leaks at all. Permatex 80019 is holding up to the ethanol blend.

Larry did have a good idea, and I did something similar. I simply had the bottom of the carb on my bench, and filled the bowl till it was 5/8" full of gas. I could then watch where the fuel weeped out of the gav fitting - which was at the top around the threads. Didn't start leaking till the fuel level in the second well was that high.

I'll post back if the 80019 fails....