Cracked NH carb gas inlet- Need Advice

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Model T Ford Forum: Forum 2017: Cracked NH carb gas inlet- Need Advice
Top of pagePrevious messageNext messageBottom of page Link to this message  By george house . . .caldwell county, TX on Sunday, August 13, 2017 - 04:29 pm:

I'm sure I'm the first dummy to try and get one more turn of that threaded brass gas inlet fixture on a cast iron carb. It'll dry off after I turn the gasoline valve off but immediately becomes wet with gasoline when the gas valve is opened. Now I've previously has good results with a Permatex product called 'Luquid Metal Filler' Item # 25909 but just visited 4 national parts stores and couldn't find it or any product stating impervious to gasoline. Anybody have any successful experience with fixing this leak? I do have a Dremel tool I could 'V' the crack.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Sunday, August 13, 2017 - 04:44 pm:

George

many of us have done the same thing...I know I have...once.

I actually had success wicking in loctite retaining compound into the crack in the casting (low viscosity variety) with the fitting removed. I think the key to success was later using permatex #2 on the pipe threads and stopping before it got tight. Has worked just fine.

Loctite has a nice write up on sealing porosity with their product, and I've worked with castings treated thusly. Though porosity is certainly different than a crack...a crack has potential for stress, and seal failure, but if you keep the joint stress-free, I think you'll have the same success that I did.

http://www.loctite.ph/php/content_data/LT1244_TT_Automotive_Porosity_Sealing_By_ Design.pdf

This of course assumes the crack is a hairline and has not opened up with the force of the pipe thread on the fitting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Sunday, August 13, 2017 - 04:57 pm:

I've seen those cracks brazed, but I don't know how well that works.


Top of pagePrevious messageNext messageBottom of page Link to this message  By george house . . .caldwell county, TX on Sunday, August 13, 2017 - 05:00 pm:

Thanks Scott. Yeah, it's a barely discernible crack on the top of the casting. What does "wick in" mean? And is the product called Locktite Retaining Compound ? I realized that JB and Permatex have greatly enlarged their product offerings but hadn't considered Locktite - a brand that I've used a lot.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Sunday, August 13, 2017 - 07:06 pm:

George

when you place a very low viscosity material against a crack and the material naturally flows in, even uphill, that is "wicking" or "wicking in", as though it were a cotton lamp wick, drawing kerosene up to the flame...
Make sense now?

It took me 2 passes at wicking material in on mine. After first time, after wiping off the excess and letting it sit overnight, when viewed under 10X magnification with a jeweler's loupe, there didn't appear to be any material in the crack. The second time, it wicked in, I wiped off the excess and the next day there was a very fine shiny reflection in the crack that was cured Loctite. That was when I knew I had it filled.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 13, 2017 - 07:24 pm:

George
Please do not take my comments the wrong way, they are not meant to be pejorative.
I respect Scott and Steve's opinion, but Holly NH carburetors (even the straight through type) are about as rare as crows.
Why waste your time and effort with questionable fixes?
Find another good like carburetor and move on?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Sunday, August 13, 2017 - 07:34 pm:

The seat for the ferrel in the carb of my model A has been giving me fits because it is in poor shape.
I finally tried some Permatex No 2 - non hardening - because it said it could be used with gasoline.
I was surprised that it worked.


Top of pagePrevious messageNext messageBottom of page Link to this message  By george house . . .caldwell county, TX on Sunday, August 13, 2017 - 08:52 pm:

I understand now Scott. Thanks for the explanation. I shall go into town tomorrow and try to find some Loctite Retaining Compound. So you didn't have to enlarge the crack with a Dremel? Just make sure it's dry and plan on a couple of wicking, huh? Then I might cover it up with non hardening Permatex # 2 Fred....
Ron, I don't believe good Holly NH carburetors are as plentiful as you suggest. I'm not a part of our throw away society. I'm a restorer. This NH is a straight through and it was rebuilt by my good friend Jack Daron....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Sunday, August 13, 2017 - 10:22 pm:

yes George, you're on the right track. In this particular instance, it will only work if the crack is very small, so you do not want to grind it out. In fact you will want to see it show up at the threads, which is where it really needs to be sealed...not so much the outside, though it will be nice if it penetrates thoroughly.

While this an unconventional fix, it is not beyond the scope of what the material is designed to do. Just remember that this is not a structural repair like silver solder or braze...simply a seal.

I only went this route on mine as I was in a hurry to fire up a "barn find" and the carb was the last thing to put on for the grand reveal. And then I broke it...YIKES! The car started, ran great, and the carb has remained on it and works fine.

If it had been brass, I would have silver soldered it in a New York second, but not being an expert at cast iron repair, my success with silver solder or braze has been less than desirable on cast iron. This was quick, cheap, and for me, successful. It is NOT something that I would suggest be done for any carb as a commercial repair, but to personally salvage what is now otherwise a ruined core, I don't think you have much to lose other than the price of the Loctite.

Be sure to get the wicking type, or "press fit" version of the compound, not the gap-filling type which is a thicker compound for filling large gaps between bearing and worn shafts.

Go on line and you'll find the right material and it will be described similar to what I've stated.

best of luck with your repair


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