In another thread the problem of a gas leak in the gas inlet from a crack in the cast iron was mentioned. This crack is caused from someone overtightening the brass gas inlet. I understand that proper sealing of the inlet connection involves proper gas and alcohol thread sealant. This sealant could be the proper gas/alcohol yellow Teflon tape, etc.
I have an excellent carburetor which has this type of crack. I need sage advise on the best way to seal this tiny, but worrisome crack. This tiny crack does not appear to be susceptible to shearing off but is definitely the source of my carburetor leak. I can see it becoming wet from that crack! No amount of sealant will stop this leak.
Stan Howe has mentioned a way to seal off this type of crack. I need some advise on how to accomplish the repair.
Silver solder, brass brazing?
I have the proper 1/8" NPT tap to use after the crack is sealed.
I "V" them out and silver solder them.
To patch it, "Seal-All" should work. I've patched numerous gas tanks with it, and they held for years.
That's only a patch job though, and I can under stand wanting to fix it the right way too.
As Jack said, Silver solder it. I then install a 1/8 pipe thread extension which I solder into the outlet. That way you don't have to tighten that threaded area so much and you still have good threads for the fuel line fittings. The extension fitting costs about a buck and is available at auto parts stores. Probably also at your local hardware store. It is 1/8 male/1/8 female, about an inch long overall.
Thanks for the advise!!
I love the idea of the pipe extension silver soldered into the gas inlet. I feel confident that it will solve the problem. Bravo!
Would it be necessary to "V" the crack if I silver solder the pipe extension permanently in place? If the "V" is advised, then is the "V" cut in the inside threaded part or on the outside part of the gas outlet?
After thoroughly cleaning and removing all traces of gasoline and petroleum residues, I would press some Aluminum Devcon Epoxy Putty (1 lb. box. Stock Number 10610. 4:1 ratio putty to activator) into the crack, then form an unbroken belt over and around the fitting. Rarely has there ever been a repair that I could not accomplish with Aluminum Devcon and as a putty, once it has firmed up slightly, it can be smoothed to a glass-like smothness with a wet finger, so once it is painted one cannot tell it has been repaired. I once repaired a leaky lawnmower block with a bad oil leak with aluminum Devcon and it never leaked oil again in the 25 years I had the mower, so, not only will it stand up to gas and oil, it will stand up to heat.
PS. If a fitting is to go into the inlet, it should be installed and tightened before the repair is done, no matter what repair medium you use. If the repair is done before the fitting is put in and tightened, the repaired crack will almost certainly expand and open up the repaired crack and repair medium covering it. If the fitting is installed and tightened and then the repair is done, there little chance of the crack opening up and the repair should hold as long as the fitting is never removed or disturbed. Jim Patrick
If you use good silver solder and good flux it will not be necessary to v it out. The solder will flow into the crack if you have the temp right. How I do it is to solder the crack, then run a tap in the inlet to recut the threads in the solder and the inlet material, then screw a short extension in finger tight or slightly tighter and reheat, run the silver solder around the threads so it flows into the inlet area. Good silver solder is pretty tough, I've done several of these where I didn't put the extension in and they held fine. I've silver soldered hydraulic pumps, carburetors, guitar parts and yesterday, a bushing in a Ruckstell thrust plate so I could machine the plate to correct size for the thrust plate. You can also braze things like this but silver solder is a little easier as it melts at a lower temp. It takes a lot of heat to run brass into a crack in a carb inlet. If you are going to do that you should use bronze rod instead of brass as it will flow into the crack and hold better than brass rod will.
Everybody has their own methods and they work probably equally well. My personal preference is methods that would have been used in the day like solder, brazing, etc. I do not use JB Weld or modern chemical fixes for anything. Others mileage varies. It is also true that many people do not have the shop I have with torches, etc., so it might be easier for them to use other methods. There is probably no better or worse, just differences and preferences. I personally trust a brazed or soldered repair more than I do some other methods. 400 carburetor rebuilds and counting.
Stan, Is there any way you could give a crash course description of brazing for those that have never done it, such as preparation of surface to be brazed, best type of gas or gases to use, most effective temperatures for best results, proper color of flame, best type of brazing rods, how to flow it, etc. Thank you.
That sounds like a great subject for the winter seminar in Hutch sometime. I expect a lot of us could benefit from seeing an experienced hand demonstrate that kind of work.
The short answer is you need an acetylene torch set with a variety of tips, temp varies by material but most will flow brass at cherry red or just turning orange. An oxygen rich flame as the carbon from a yellow flame will contaminate the area. Flux coated brass is easiest to use, dip flux gives less dross and a cleaner weld. I do a lot of brazing of cast with some old liquid flux that I don't know what it is, a bottle I got in some soldering stuff at an auction, seems to work, it's probably acid of some kind. I personally like bronze rod as it is copper/tin as opposed to brass which is copper/lead. Any welding shop will have the equipment and supplies after that it is practice. Bronze that is hot enough will flow just like solder into a crack in cast iron with flux on the iron. Bronze will also stick to cast better than brass tho is not as easy to weld with because it melts hotter but the tin in it acts just like solder when you do get it to melt.
I guess the main thing is you can't stick brass or bronze or solder to anything that isn't hot enough to melt whatever you're trying to stick to it. HOT is the trick. Get a good set of goggles so you can see that bronze melt and it will flow right into a hot crack.
I took a couple years of night school welding classes about 35 or 40 years ago when I first moved to Helena, when I got done with them I could weld anything but a broken heart and the crack of dawn. Now I struggle to lay a decent bead with a wire feed, let alone a pretty weld with an AC stick or hammer welding with gas. Lack of practice and I don't weld much. I have three gas torch sets plus a big MIG/TIG/DC Stick Panasonic Gunslinger 260 and should be able to weld anything but I have to practice before I do anything I need to have look decent.
Thank you, Stan. Merry Christmas to you and yours from me and mine. Jim Patrick
The most important thing to great welding is 'practice, practice, practice'! And it is not like riding a bicycle. The equipment I have is a 60+ year old acetylene torch in fair condition and a 50 year old Lincoln AC arc. I learned how to weld on these pieces when I was about 12. I also had some professional training after I got out of high school. My problem is I don't weld often and consistently enough. I do a bunch of welding for six months or so, and just about the time I get really good, I don't weld again for two or three years.
Thank you, Stan, those tips (hints) will help with one of my welding projects coming up right after the holidays.
Drive carefully, and enjoy the season! W2
One thing to add to Stan's post, keep the pressure low on the regulators when brazing to keep from burning the bronze. If sparks fly up when you heat the bronze, it is burning and will leave a porous weld. Dave
He said: "..... I could weld anything but a broken heart and the crack of dawn..."
That Stan is a man of many talents - including literary...when the shop gets too cold, he will always find something to do in the warm house.
Time to write another adventure of Herman & Freida, or maybe another song this winter?
Merry Christmas and a Healthy New Year to you Stan, and all the Forum readers.
My definition of silver solder is silver brazing using an alloy like Harris Safety Silv 45 which melts at around 1100F or so.
Stan, Jack is this what you use?
I don't think so. The stuff I have came on a roll in a box of stuff at at auction years ago. It is now down to a little stub. I'm going to have to buy something pretty soon. I'll see if I can find some of the Harris.
Dave, thanks. That is a result of being self unemployed for most of my life and growing up so damn poor we had to do everything ourselves or it didn't get done. I inherited my Grandfather and father's "fiddlefooted" tendencies and am a jack of all trades but master of none for sure.
As far as Herman and Freida, there are a couple new stories churning around and "Einar and Torvald Go Racing" is about half done but I don't see a day to work on it in the near or even fairly distant future. Still trying to make a living. You can, Howvever, sing the same song I wrote last year that was in the Vintage Ford.