Fixing a Ruptured Bore in my Weber Carb.

I was hoping I could get some advice on fixing a ruptured bore on my 44 DCNF Weber carburetor.

As things stand now, I have the aluminum zinc soldering rods to fix the rupture. My concern regards the proper way of heating up the stripped down carb. body. I have been told that using a propane torch is a bad idea. So how else does one allow the solder to melt? Also, I have been told that to properly solder aluminum one needs to slowly heat up the aluminum, solder, let it cool down, then slowly heat up again. I suppose that that is a doable thing with a torch, would it not? I was suggested that the bulk of the carb body be placed in water to protect the integrity of the lead plugs. It makes sense, but is it the correct way?

What metallurgical principles are at work here, I would like to know.

Has anyone ever done anything like this before? Thanks in advance!

Ciao,
George

 

What ruptured is this, the air/fuel mixture screw was over tightened. The tip of the screw when fully engaged seals the small tappered hole to the barrel and is located directly under the throttle plate.

The aluminum zinc solder will adhere and in fact be stronger than the parent metal. The rupture around the screw tip is probably 4 mm in diameter. Granted aluminum is porous, but it cannot absorb gasoline. Once the surface is filed/Dremeled and prepped it should be a done deal. My question is not will it work , but rather what is the best approach to doing this.

I have a scrap carburetor to work on, so I will practice on it and see how things go before I start on the Weber.

Ciao,
George

 

The Alutite [aluminum zinc soldering rods] will not adhere to any ferrous metals. The A/F mixture screw will be turned in the same distance as the opposite barrel A/F screw for a fully closed position. The surfaces will most likely be hand filed to be sure the surface is clean from impurities with a final cleaning of denatured alcohol.

Once the solder has cooled, the screw will be backed out and the seat/bore will have a perfectly matched taper. I will just have to see how it all works on the junk carburetor. I suspect that since it is such a small area, it should heat up quickly with little heat transfer to other areas such as the plugs. Time will tell.

BTW nice job on the carburetor flanges....clean.

Ciao,
George

 

Hi Bob,

Happy New Year.

I contacted the Evercoat [Metal To Metal] and USC [All-Metal] people in regards to its appropriateness for gasoline contact. The answer was no. Both of these materials must ultimately be sealed, and they contain approximately 15% talc as well.

I used JB Weld. It is designed for contact with gasoline. When the pressure of the screw was applied to this 4mm patch, the JB Weld would bow out. Totally unsatifactory. Actually, removing it was quite easy.

Alutite and it's American counter part Durafix have a melting point of about 700F. I ought to be able to heat up and fill a 4mm hole rather quickly.

Check out the videos at Durafix and see what you think. BTW a friend of mine has used it on aluminum parts with excellent results. This might be a first for a DCNF Weber.

Caio,
George

 

Bob,

Muggyweld IIRC is also an aluminum/zinc alloy with maybe some other things mixed in with a resulting lower flow out temp. of approx. 300F [Soft Solder]. The Durafix and Alutite have a higher melting point of approx. 700F [Hard Solder]. No flux needed with these two.

The Webers are aluminum with some zinc. The melting point for the carb material is around 1200F. So getting it to 700F with a propane torch should not be too difficult. Insulation of the carb body will also be a key consideration during this process.

If you Google Durafix, you can see some interesting demo videos as to how the whole process works.

As in my case, the 44 DCNF falls into the unobtanium catagory, so my only option is to fix it.

Magnesium is a whole different universe. This is a highly volatile and dangerous metal when exposed to a flame. Mangnesium even in alloy form could be problematic, I would venture to say! Just to check, get a small shard of this metal you believe to be magnesium, put on some protective eye wear, and put a torch to it just to confirm that it is in fact magnesium. Then for sure you will know what you are dealing with.

There should be absolutely no corrosion/rust issues since the solder only bonds to non-ferrous metals.

Ciao,
George

 

Thanks Mark,

Appreciate the feedback/info.

Ciao,
George

 

As a matter of fact I did speak with the Pierce Manifold folks. The discussion that we had did not satisfy me.

As far as patching up the carburetor. I think it would be fair to say that using JB Weld would be a patch. You are using some sort of gas resistant catalyze material that is not even metal AFAIK.

In the case of Durafix and Alutite you are using an similar aluminum alloy that will bond on a molecular level with the parent metal. When you weld to pieces of metal you certainly don't think of that as patching a hole with buble gum, but rather a significant joining of metals. Well, the difference between welding and soldering is a temp.difference. Soldering is bellow 750F more or less, and welding is executed at a much higher temperature. Secondly, when one welds the parent metal is melted along with the filler metal, where as in soldering, only the filler metal/alloy is melted. Final result is a part that is as good as new.

Ciao,
George

 

It appears that I have exceeded my attachments limit. I'll PM it to you, and you can post it, if that works for you.

Ciao,
George

 

Hi Stu,

The downside of Muggyweld for me is that this alloy solder bonds all metals. For you it's an upside and sounds ideal for your oil pan, especially with the lower working temperature.

With the A/F mixture screw engaged into the carburetor it will act as template for the bore/seat. Once the alloy solder is cooled the A/F screw will easily back out. Not so with Muggyweld it would seal everything shut.

The prime consideration is warpage at this point. I am ordering a quart of Anti-Heat Compound from Eastwood. I will literally encase the carburetor in this compound. Since this area is so small I will use a butane micro-torch. A friend of mine has told me that this will take about 90 seconds to complete.

Paul, thanks for the advice on doing a reheat once installed. I am hoping that will not be needed.

Of course as I said before, I will practice and practice on my junk carburetor to get a sense of how fast thing heat and flow.

I'll post my progress as things develop.

Ciao,
George