Carb Casting Repair, Zinc Solder?

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HDBD
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Carb Casting Repair, Zinc Solder?

Post by HDBD »

I am looking to fill a hole in a carb casting. OK I know it is zinc and where this gets a little dicey, I want it to be undetectable. I will metal finish it and then chromate the casting to get back to the original color. Some aluminum alloy will not work. I am looking for some sort of low temperature zinc (primarily 80% or better) rod to braze with. Thoughts?
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Re: Carb Casting Repair, Zinc Solder?

Post by tjs44 »

Maybe call Sean at SMI in huntigton beach CA of what to use?Tom
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Re: Carb Casting Repair, Zinc Solder?

Post by Geoff2 »

Probably better off contacting a panel shop that restores older cars that used zinc castings for emblems, tail light housings etc.
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Re: Carb Casting Repair, Zinc Solder?

Post by Baprace »

HDBD wrote: Fri Apr 23, 2021 11:11 am I am looking to fill a hole in a carb casting. OK I know it is zinc and where this gets a little dicey, I want it to be undetectable. I will metal finish it and then chromate the casting to get back to the original color. Some aluminum alloy will not work. I am looking for some sort of low temperature zinc (primarily 80% or better) rod to braze with. Thoughts?
Why not use a 2 part epoxy , simple to use and will last forever. JMO
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Re: Carb Casting Repair, Zinc Solder?

Post by HDBD »

Fixing is one part of the issue. this is a valuable rare casting and I need to then restore the original dichromate gold look for authenticity reasons
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Re: Carb Casting Repair, Zinc Solder?

Post by underhead valve »

I have made repairs with the rods they sell for fixing pot metal to make about a square inch of fuel bowl bottom ,used some rusty metal to make a form for the bottom melted it in, it looked somewhat ugly but was still working 15 years later, perhaps if I had practiced some it could have been nicer looking
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Re: Carb Casting Repair, Zinc Solder?

Post by Kevin Johnson »

I would ask on specialist forums that do plating. WAG that you could electroform copper to fill the hole -- polish/finish it and then plate it. You will need advice on masking, solutions, etc.
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Re: Carb Casting Repair, Zinc Solder?

Post by jsgarage »

HDBD, if you use zinc or pot-metal rod to weld the thing, be prepared for pinholes. Zinc is even worse to weld perfectly than cast iron- which for me is only for magicians with all their dues paid. So at some point you are gonna have to consider fillers. Grind a piece of another carb and mix the grindings with a transparent epoxy to make a filler with the right color. Some chromate coatings will bridge over small filler repairs. Good luck.
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Re: Carb Casting Repair, Zinc Solder?

Post by Walter R. Malik »

If it is that important or that valuable then send it somewhere who does ZINC welding.

Years ago when engineering new carburetors Holley had people who could weld just about anything Zinc ...
I am sure there are places to do this.
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Re: Carb Casting Repair, Zinc Solder?

Post by VMC »

I restore carburetors for a living, maybe I can help.

If you'd like, shoot me a PM.

Eric
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Re: Carb Casting Repair, Zinc Solder?

Post by hoodeng »

Looks like VMC is going to be your first port of call.

As a point of interest HDBD, what make and year is the carburetor you are working on?
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Re: Carb Casting Repair, Zinc Solder?

Post by HDBD »

Bringing this to the top.
Working on a Holley list 3124 dated 1965 L78 396 carb . Choke housing got hit and bent, small piece is cracked at the top.

I have found 99% pure zinc solder and successfully got it to bond with the base metal experimenting with a scrap core. The base metal needs to be molton and a very direct small flame is needed. The casting needs to be supported as it wants to fall into itself if I am not extremely careful with the heat. It takes a technique moving off when there is a sign that the casting molton area is growing. Very delicate work. I wish I could use TIG but IME striking a torch to the zinc casting just spews black impurities, even at low heat with small tungsten and cup. I also wish there was a flux I could use. Was thinking about using borax as an experiment. Not sure about the boric acid. Have used Gasflux, type FB3-K, with straight acetylene to production braze steel but couldn't justify this here as these are occasional jobs and the equipment and fluid I used is long gone plus no idea if it is compatible.

There aren't too many guys around any more that get this stuff. I have a friend, 86 now, that worked at Chevrolet on the original Corvette Ramjet cars. He is an expert. Sure would like to find an expert to fix these castings. I am a little gun-shy to dive in, to be honest.
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Re: Carb Casting Repair, Zinc Solder?

Post by rgalajda »

VMC wrote: Wed Aug 25, 2021 4:45 pm I restore carburetors for a living, maybe I can help.

If you'd like, shoot me a PM.

Eric
What are you using on the body of the carb?
The body of this carb looks like it was Zinc plated , and then chromate applied, which would not be correct. Only the steel parts would have been done this way originally. The body of the carb should be chromate only , this would be less shiny.
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Re: Carb Casting Repair, Zinc Solder?

Post by VMC »

The castings weren't zinc plated, they were stripped (proprietary process) and chromated.
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Re: Carb Casting Repair, Zinc Solder?

Post by Tuner »

rgalajda is right, the color is too bright yellow gold for a restoration carb. OEM carbs, and particularly Fords, were a darker bronze color. I think if you add more chromate to the bath it will produce a darker color. The Caswell book refers to adjusting the color by changing the concentration of chromate.
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