TR2/3/3A Leaking SUs. Advice badly needed

[PatGalvin]

OK Guys. So, I had my SUs rebuilt a couple years ago and they sat in the box until I got ready to install them. They both leaked gas. I purchased Joe Curto's jet kits and installed. The front SU leaked still leaked through the connection between the bottom of the float bowl and the carb body. The rear SU leaked thru the jet. For the front SU, I purchased a new float bowl mounting stud (number 123 in attached graphic) and fiber washer (Number 124) from Moss. The existing stud looked like maybe it was deformed due to overtightening so I thought a new stud might seat better. I installed the stud with a little RectorSeal No. 5 which is fuel-resistant non-hardening pipe thread compound. The rubber seals that sandwich the float bowl mount were about 2 weeks old (Curto kit) so I didn't replace again.

The back carb was fitted with new cork jet locking gasket and two of the Moss O-Rings replacing the cork jet seals. It appears to have sealed up nicely so I'm pretty happy about that.

So, the front carb still leaks badly, at the connection between the carb float bowl and the carb body. I get a one drip per second . It is very difficult to tell where the drip is coming from but it is either the connection of the mounting stud to the carb or the rubber seals that sandwich the float bowl mount.

I really need to get this car leak free before next weekend. Can anyone provide suggestions as to how I can address this leak under the carb body at the float bowl mount? I'm open to any suggestions. Very perplexed...

Pat

 

[sp53]

I might suggest checking the thickness of the metal washer that goes on the stud for the bowl. If the washer is too thin, the nut will bottom/run out of threads on stud before it seals on the stud. You probably need a thicker washer on the stud.

 

[PatGalvin]

I might suggest checking the thickness of the metal washer that goes on the stud for the bowl. If the washer is too thin, the nut will bottom/run out of threads on stud before it seals on the stud. You probably need a thicker washer on the stud.

Would it make sense to double up on the washer (either top or bottom) to increase the squeeze on the viton upper and lower gaskets. I really don't have any way of knowing if the crush on the viton seals is adequate, but I can say that the float bowl will rotate fore and aft a bit, when installed. So perhaps we do indeed need to add another washer or two?

Any other thoughts? Anyone have problems with the stud sealing on the carb body?

 

[tinman58]

Hey Pat!
Install a supercharger, problem solved.

 

[Jerry]

We bought parts 89 and 102 for Ian's MG TD which have the same carbs. That stopped the leak. The kit 89 includes all new brass parts so there was not too much slop, or , the slightly different pre-soaked seals in the kit worked.
Poor design, my old TR3 leaked all the time. took the paint off the car below the carbs.

Jerry

 

[PAUL161]

but I can say that the float bowl will rotate fore and aft a bit, when installed.

I'm sure you realize the bowl should not be able to be moved when the bolt is tightened and sealed properly.

 

[PatGalvin]

I called Joe Curto this AM to see if he had any ideas. He recommended a couple things. First, the Viton grommets that hold the float bowl mount should be installed dry - no oil or lube should be used. If slippery, they may deform and not fit as intended. I used a little oil on mine and that is not a good idea. He is sending a little fiber washer that I can add below the steel washer (that sandwich the Viton grommets) to increase tension on the Viton grommets. Finally, he said that a little Permatex Aviation Gasket sealer can't hurt on the mounting stud and fiber washer to carb body connection.

Hoping these changes will make a tight seal. I'll let you know. And, I hope this is helpful to someone out there in LBC land.

Pat

 

[TuffTR250]

Pat, on my TR3 I put all new washers, etc, and it still leaked. I cut a washer shaped piece of gasket material from some gasket material I got at CarQuest and added that to the viton rubber seals and that stopped my leaks from the float chambers. Those viton seals are either too soft or not think enough. I tried the fiber washer's you're getting from Joe Curto and they did not help. They are too hard.
Regards,
Bob

 

[PatGalvin]

Pat, on my TR3 I put all new washers, etc, and it still leaked. I cut a washer shaped piece of gasket material from some gasket material I got at CarQuest and added that to the viton rubber seals and that stopped my leaks from the float chambers. Those viton seals are either too soft or not think enough. I tried the fiber washer's you're getting from Joe Curto and they did not help. They are too hard.
Regards,
Bob

Thanks Bob. Do you remember approximately what thickness of washer/gasket material you used for the "spacer"?

Thanks for the tips.

pat

 

[TuffTR250]

I used Victor Reinz gasket material p/m JV127 from CarQuest. I measured it and it is about .032 inch thick. Using the Moss catalog as a reference, I found that the float bowl mounting bolt #115 did not work well at all. I went to stud #123 since It did not have to turn inside the viton seals in order to tighten it. Here is the sequence I used that was successful in stopping the leaks: from bottom up: 120, 121, 118, bowl flange, 118, 122, 123, 124, home made washer from JV127, bottom of carb.

If you have bolt #115, I'm not sure how to stop the leaks since I was not successful in stopping the leaks with that type mounting.
Good luck with it!
Regards,
Bob

 

[PatGalvin]

Thanks very much for all the info Bob. I pulled the offending leaker last night and cleaned all the parts carefully with brake cleaner. I used a permatex Permashieldl product (similar to Hylomar) to seal the stud and fiber washer to the underbody of the carb. I reassembled the viton grommets dry, with no oil. I reinstalled and manually pumped the fuel pump to fill the bowl. No leaks yet. Was dry this morning when I was leaving for work. Let's see if it will stay dry....

The Permashield product seems just like Hylomar. And you can obtain it at FLAPS. Around ten bucks.

I'll report back after I run the car this weekend and see if it is leak free.

Pat

 

[TuffTR250]

Sounds good! The Permashield is sealing in the same place mine was leaking. I used the gasket material instead of a sealant at that spot.
Regards,
Bob

 

[PatGalvin]

Hi Guys
Very old post, but update that I thought some of you may find useful. I was again having leakage from the float bowl mounting to the bottom of the carb body. Leaking at the two viton seals that crush around the float bowl mounting arm (that's what I'm calling it...).

I did two things to make this not leak any more. First, I bought new Viton seals and they are different than the ones I was using previously. The replacement Moss Viton seals are solid and don't have a groove cut into them. See attached photos. Solid seals crush a lot better and don't deform as much, holding the bowl much tighter. Second, I added a couple small shims (like very thin washers) to the top of the mounting stud, increasing the crush on the two washers. The combination of these two things made this very tight and leak free. I just added two 0.010 shims from McMaster Carr - Cost me $10 for the shims but I figured I'd keep adding them till I got the viton gasket crush I needed.

Hope this helps others that may be struggling with fuel leaks from this location.

Pat
this viton bushing has a groove cut in it (from Joe Curto, I think).

This Viton Bushing is solid, like a garden hose washer.

McMaster Carr Shim Set.

 

[Brinkerhoff]

Have you checked the aluminum sealing faces for scoring? Either side of the float bowl and the bottom of the carb body.. I don't remember having any leaking with mine at all.

 

[PatGalvin]

Yep, sealing faces were clean and smooth. I just wasn't getting the compression I needed on the Viton bushings, especially with the grooved bushings. Hope this helps others, at some point.

pat

 

[Brinkerhoff]

Great ! Its the little things that take a lot of time to correct but even more satisfying when you do.