The Carburetor Shop LLC

204 East 15th Street

Eldon, Missouri 65026

 

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Carburetor Finishes

General

Unless one has a copy of the original drawings or blueprints, trying to recreate original style finishes can be difficult, AS MANY FINISHES WILL CHANGE WITH TIME, AND EXPOSURE TO LIGHT! As an example, I was convinced that the vacuum motors used by GM on their late 1950’s and early 1960’s tripower were white zinc, from looking at new old stock components. Until one day I disassembled one of these, and found that the finish that had been protected by some of the hardware was undeniably yellow zinc. The yellow conversion coat for either zinc or cadmium will fade, and with time become completely transparent!

One thing to remember about finishes is that for the most part, the carburetor finish was for metal protection; NOT to make the carburetor look “pretty”. There are documented exceptions to this such as the 1930’s Packard, and some Cadillac carburetors, and the more modern turbo Corvair carburetors.

The finishes listed below are my BEST GUESS at this time, based on 40 plus years of experience, and custody of many original drawings and blueprints. If any have drawings or blueprints which will conclusively prove otherwise, I would delight in seeing them, so that I can make this page as accurate as possible. As we do not work on carburetors newer than 1974, we have no way of knowing if later finishes differ.

Carter  |  Rochester  |  Stromberg  |  Zenith

Carter

In general, finishes on Carter carburetors were for metal protection, not appearance. Notable exceptions would be the WD-0 carbs used on the V-16 Cadillac, and the YH carb used on the turbo Corvair, both of which had black paint applied over the normal body finish, and chrome steel linkages. Carter Carburetor Company was located across the street from Crown Plating. Carter had an anti-corrosion specification for steel pieces which would have been met by using any of the following electroplatings: white zinc, white cadmium, yellow zinc or yellow cadmium. As the steel pieces would arrive at the plant from the stampings plant, they would be sent across the street to Crown, and electroplated with whichever of the 4 finishes Crown was running that day. Since Crown ran more white zinc that anything, more of the Carter steel pieces are plated with white zinc than the other finishes. However, I have seen new Carter carburetors, which had steel pieces representing all four of these finishes. Carter used the chromate finish on zinc allow, aluminum was left natural, and cast iron was “iron phosphated”, and then painted with a “special” body paint. Mostly, this paint was black (about 60 percent gloss), but brown and gray were used on certain carburetors.

Rochester

Finishes on Rochester carburetors were for metal protection, not appearance. Zinc alloy castings were given the chromate treatment. Steel pieces were treated with yellow zinc, or black oxide up until the late 1960’s. Beginning in the late 1960’s, some linkage (steel) parts were coated with teflon. There is some disagreement whether the choke plates and air valve plates should be electroplated with white zinc or yellow zinc. As mentioned earlier in this article; the yellow conversion coat will fade and turn transparent with time. I have disassembled new old stock quadrajets, and found yellow on surfaces, which were protected by screws, when the exposed surface was neutral. Thus, until confronted with hard evidence (original drawing or blueprint), I will believe these items should be electroplated with yellow zinc. As these components are covered with the aircleaner when the carburetor is installed, no points should be deducted regardless of the finish on these items. Screws from 1949 up until about 1955 were yellow zinc. Sometime about 1955, screw finish was changed to black oxide. Cast iron was treated with “iron phosphate”.

Stromberg

Stromberg carburetors were used on many expensive cars in the 1930’s and many of the finishes were used for both protection AND appearance. Many Stromberg bodies were painted black, and while the standard electroplating was zinc; many other finishes i.e. dull nickel, bright nickel, and chrome were used. We have most of the original Stromberg drawings available for sale. Zinc alloy bodies were treated with chromate; cast iron was treated with “iron phosphate”.

Zenith

Finishes on Zenith carburetors were for metal protection. Cast iron was treated with “iron phosphate”; zinc alloy castings were treated with chromate; and steel pieces were electroplated with white zinc.

Electroplate

This is a process of covering a base metal with another metal by submerging the base metal in a solution containing the cover metal and running electricity direct current through the metal. Ion flow from the solution to the base metal will coat the base metal with a thin coat of the cover metal. While there are “hobby” electroplating outfits available, the home enthusiast should be aware of both the dangers of fumes emitted in the process, and local ordnances. DO YOUR HOMEWORK!

Chromate

The chromate treatment is a cold treatment applied to zinc alloy castings. The castings are first chemically cleaned in caustic lye; washed in water to neutralize the lye which is a “base”; and then dipped in a solution of nitric, sulfuric, and chromic acids. The surface of the zinc alloy is chemically “etched”, and the residue is a very thin cover coat, which is a greenish goldish cover. This process is done to minimize the formation of zinc oxide of the metal. WARNING! This is not a process that the hobbyist should even consider!!! The active ingredient, chromic acid, is a known carcinogen! THIS STUFF IS DEADLY.

Conclusion – and advice to the hobbyist! We evaluated the cost, convenience, and danger of these chemicals long ago. We feel that, even with the number of carburetors restored by The Carburetor Shop, that that number is insufficient for us to attempt to do any of the electroplating and/or chromate coatings ourselves. We send everything to various “metal laundry” companies for this service. We highly suggest that hobbyists should consider doing the same. This article is placed on the web to discuss what finishes the restorer should be aware of (for points judging and protection); NOT as a do it yourself treatise.