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I'm running two Rochester one barrel carbs on my 37. I bought them as advertised because they were NOS. I think they are, but I continue to have one problem, especially, if the truck isn't started and driven for a few weeks. The fitting on the carbs that is screwed into the pot metal carb top has a small round gasket between the brass fitting and the pot metal of the top. Obviously, you must not over tighten the fitting. I can got it tight enough to work when initially installed, but after a several months it starts leaking fuel which runs down on the manifold and onto the headers.
Can anyone give me a suggestion as to how to fix this problem?
As always, your help is appreciated!
Joe

On my '50 I used a couple wraps of teflon tape on the threads of the fitting that goes into the carb top. I know that its not recommended to use teflon tape on fuel. I was careful and made sure that I stayed back one thread before I wrapped the threads. Its important that if you take the fitting out after using the tape on it you clean the stuff out of the threads before you put it back together so you don't push stuff into your carb. Don

Permatex #2 works well if the pipe threads aren't opened up too much. I agree with Denny: no gasket.

cm

All good advice. The threads are 1/8 not 1/4 pipe threads. I always use Teflon tape. Sometimes you can find a fitting that is not threaded back as far.

I disagree. All NPT threads are designed to be used with a sealant. For metal to metal seal NPTF (dryseal or AKA National pipe thread-fuel) thread form should be specified. From the machinery’s handbook:


American National Standard Dryseal Pipe Threads for pressure tight joints—

Dryseal pipe threads are based on the U.S.A. (American) pipe thread; however, they differ in that they are designed to seal pressure-tight joints without the necessity of using sealing compounds. To accomplish this, some modification of thread form and greater accuracy in manufacture is required. The roots of both the external and internal threads are truncated slightly more than the crests, i.e., roots have wider flats than crests so that metal to metal contact occurs at the roots and crests coincident with, or prior to, flank contact. Thus, as the threads are assembled by wrenching, the roots of the threads crush the sharper crests of the mating threads. This sealing action at both the major and minor diameters tends to prevent spiral leakage and makes the joints pressure tight without the necessity of using sealing compounds.


Joe,

Grinding off the first few threads may prevent bottoming out and I have the best luck with fuel fittings using Permatex Aviation form a gasket # 3.

Denny Graham wrote:
I don't think any of the 'B's had a fitting with a gasket till the later models when they added
the sintered bronze filter to them.
___________________________________________

These units DO have the bronze filter in them and consequently have the small round black gasket fit on to them at the point where the carb and the fitting go together. There are some thing about a Stovebolt I don't like - not many but a few, like this one!
Thank you and the others for your replies.Good suggestions and I will take ALL of them into consideration as I return to the task of repairing the leak.
Thank you, again!
Joe

Well, I dinked around with this thing all afternoon and I can't get any good results.
If you actually try to get enough pressure to seal the joint by tightening the large brass bushing, which is what it really is, it pops a tread and still won't seal with the washer supplied from a rebuild kit. That, of couse, is not good.
So I got a plan. Tell me if I'm making a mistake, as I will not do anything until I get some opinions.
Since the bushing which goes into the carb is a 3/8" thread, I have tried to put a 3/8" pipe thread cutter into the opening. It will start nicely and tighten up, nicely, as a pipe thread should. So, I think I'm going to pull both carb tops and re-thread that fuel line opening to a 3/8" pipe thread and go to a 90 degree 3/8" pipe thread male into that hole with a 1/8" compression fitting female onto the fuel line, which I did have on that end with the other (bushing) fitting.
Anyone see any problems with this idea?
Again, Thank You!

Denny -

Thanks for responding to my post.

I still have 7/8-20 threaded hole. My comment was that a 3/8 pipe tap tool fits into the 7/8-20 hole (because it is tapered on the front end and the threads are very similar) easily. A rethread may be possible, but I'm not sure that is the thing to do.
The real prolem is that the washer they supply you with to seal the brass fitting just doesn't seal the fitting. I guess I'm looking for another kind of washer that will seal and for any other suggestions for another way the seal could be maded. There is a 1/8" pipe threaded plug around the corner from the brass fitting (facing the engine) and it could be used. That would give you a set up like the older Rochesters, but that still doesn't help stop the 7/8 subject hole from leaking.
I need ideas !!
One other question - I looked for some Pernatex #2 sealent and can't find it. I did find some whiteish stuff that Permatex makes for sealing threads. It's in a plastic container with an applicator brush. Can anyone tell more about Permatex #2, please.

Thank you, Sir!

I was afraid I would end up with a stripped out inlet on this carburetor! Dang - and it's an exact match to the other carb.
Does anyone have an idea how I might be able to salvage the top to this carb? It does have another fuel inlet for a 1/8" pipe adjacent to the large inlet that I could use, but how can I plug the large hole considering it is stripped out.
Any help or ideas are appreciated!

There used to be self threading o-size fittings available for those. I imagine you can still get them.

A quick Internet search, using the words George provided
comes up with a Tomco tech tip. It's not for the 1bbl, but maybe they can help.

Scroll down to Carb problem solvers.

http://www.tomco-inc.com/Tech_Tips/ttt7.pdf

Joe,

If resorting to an epoxy repair I would suggest this product with excellent fuel resistance which you should be able to find at most industrial distributors.

Joe,

The pics of your engine, along with your attention to detail, gave me some good ideas.

Hope all works out and you find a way to fix that leak.

Wanted to report that I got the problem fixed. Here is how I approached the problem and what I finally did:

I tried to use a 5/8-18 tap to clean up the carburetor inlet threads. A 5/8-18 will not work. I went to the hardware store and found that the only fitting that would even screw into that hole is a flare fitting, but I don't know what size and it was and it really wasn't going to do me any good since even at that it fit loose, so I really didn't have anything to go with there. Besides that, the carb is not set up for a flare fitting. I finally found that a 3/8 pipe tap started into the hole and went in almost as well as a 5/8-18 tap, but stopped just like the 5/8-18 tap did but, as you know, the pipe tap has a natural flare to it and can be tightened to stop a leak. So, I took a deep breath and used a 3/8 pipe thread and did a re-thread on the hole. I then went to the hardware store and got a 3/8 to 1/8 pipe fitting and slowly tightened it into the hole. The fuel line is set up with a pipe tread on one side and compression fittings on through back to the fuel pump.

It's fixed and is working great and now I don't have to mess with that little funky paper gasket that is supposed to handle the problem.

Thanks to all for the suggestions and help !!

seems like a lot of work to fix something so cheap and readily available.

I had kinda the same problem w/my 63 rochester model B. Mine was 7/8 into the carb and 5/16 inverted flare coming off the fuel line. Alot of auto transmissions use a 5/16 inverted flare fitting. Worked for me.

I'm curious, brokenhead, as to what you are talking about. Can you explain so I and others can learn?

Thanx.

you can buy rochester carbs and parts all over the place, just look on Ebay, any of the parts for sale forums, Craigslist has netted me an entire engine, and transmission with all the accesories (starter, and generator)for $100, just casually talking about the truck at work I have had 2 people give me carburetors. I have 3 rochesters in my garage. From my point of view it is like repairing a pencil, just get another one, then you will have spare parts. But you have to be careful some people seem to think just because it is old it is worth a lot of money, when in reality, its just old, they are not rare by any means. So you will have to look around a bit, but you can usually find one for $20 or so. And if all you are after is the top with a sound inlet connection, the rest of the carb doesn't matter. However I definintely understand the pleasure and pride that can come from repairing stuff, but whatever you do to the carb from this point will render it "modified" and not original any longer. There comes a time in any piece of equipments life when it is no longer useful, and becomes junk. I mean if you were on the moon or something, you would have no option.

I agree with you, in many cases. I have had people give me "parts", also, but when you have two perfectly matched by the numbers, by the casting, NOS Rochester carbs, I will guarantee you, they aren't just laying around the wrecking yards or swap meets. Read what I wrote - "perfectly matched" for a smooth correctly carburetored engine. As far as altered, as long as they are equally altered, I have no problem with that, especially if it is an improvement.

Now, if you just want some Rochester carburetors - I have about four crates of them and, you guessed it, not a one matches any other. I collect them and work on them and it is a rare find to find two that match correctly and perfectly. The other thing I always hear is that it's hard to tune them and keep them "running right". Another incorrect statement, if they match, they will "run right". And if you have any sets of two that are NOS and perfectly matched, with matching numbers, I'd be interested in hearing about them. Based on your comments, I'd expect the price to be right.

If they're available like they might well be, I want three of the big bases used on the 261 chebby truck engines, it looks like the 'body' is the same and the tops are often different. They look like they will flow lots of air as compared to the zeniths, I don't see they can be very difficult to make work right, there's not much there!
cheers;
ROAR

well there ya go then, I would have understood if you had actually said "Perfectly matched for a smooth correctly carbureted engine" which is probably what you meant when you DID write "exact match to the other carb", which means you have 2 identical carbs out of a whole batch of identical carbs still out there. Now if you are after NOS stuff, of course you won't find them, they haven't made them for 70-80 years, I immediatly discounted that little technicality, as you could have possibly gotten the last 2 NOS '37 carbs left in the world. It isn't even reasonable to think you would find more.