Buffing Soft Metal Carburetor Parts

Story and photos by John Gunnell |

At last August’s “Masterpiece of Style and Speed” in Milwaukee, Wis., I stood and marveled at the jewel-like S.U. carburetors gracing the V-12 engine in a 1938 Lagonda owned by Frederick L. Berndt. Later, I looked up Mr. Berndt, who told me that his car was restored by a man in Canada, but that he had rebuilt the engine and mechanical systems himself.

    He told me that he had been a Buick dealer for many years and enjoyed working on cars. He said that buffing the aluminum carburetor parts to look almost like chrome was a matter of investing the time that was needed to do the job right. He suggested that anyone with patience could do the job. I decided right then and there that I needed to add buffing rouge to my supply cabinet and a buffing motor to my shop so that I could learn the “Old World” skills that made Fred’s carburetors look so good.


After seeing the S.U. carburetors on this 1938 Lagonda owned by Fred Berndt, I decided that I had a goal to shoot for in my own restoration. Fred told me that patience is a virtue anytime you’re buffing soft metal.

    The first thing I learned is that buffing supplies can’t be purchased just anywhere. I tried discount department stores, auto supply stores and then had the idea to go on the Web. That led me to my old friends at Eastwood, which was right on the top of Yahoo’s “hit list” of companies that sell buffing equipment and supplies. I probably should have thought of it earlier, because it then dawned on me that Eastwood actually started long ago as a buffing products supplier. From that acorn grew the mighty oak we have today.

    Soon after calling Eastwood, a shipment of boxes arrived and it wasn’t too long before I found myself struggling with which corner of my crowded shop could accomodoate a /3 hp buffing motor. Thankfully, the pedestal-mounted motor did not take up much room. Even more thankfully, it came with a CD that gave me a look at the basics of buffing. I’ll admit that the CD helped me in writing this article, but I’ll also admit that I jumped into buffing my carburetors before watching the CD.


Here are the front and rear carburetor bodies, suction chambers and portions of the linkage after cleaning and buffing. The float bowls and overflow tubes are not installed at this stage.

    That’s right, I was a little anxious! And while I did not do a perfect job my first time up, I did not ruin anything or hurt myself either. That should tell you that buffing car parts is not all that difficult. With normal shop skills, a few safety precautions and a dose of common sense, you should be able to get good results. Then, if you want to upgrade to great results, you can buy some buttered popcorn and curl up to watch the movie.

    The buffing motor came with illustrated instructions and charts that help you select the right wheels and buffing compounds. Even a person like me, who skips the CD, will find himself reading the printed material. Otherwise, you’ll be wondering about how to get some of the buffing compounds out of the tubes they come in. It’s true that certain compounds slide out easily, but getting others to leave their tube is like trying to open a tight-fitting olive jar lid.


The Eastwood 1/3-hp Premium Buffing Motor mounted on the Buff Motor Stand takes up very little room in the shop.  It runs on 120 volts and spins at 3,600 rpm. A spiral sewn wheel is on the left, a loose section buff is on the right.

    There are different compounds and different wheels for buffing different types of metals. The S.U. carburetor parts are made mainly of aluminum. However, certain parts, like the overflow tubes and linkage arms, are brass or copper. All of these are soft metals, and the techniques use to buff soft metals are the same.

    Safety and buffer location are the first things to think about. The buffing motor spins at 3,600 rpm. It can shoot a part across the room so fast you’ll think a slingshot dragster just flew by. I spent half an hour looking for one brass overflow tube that the machine sent whistling past my ear. When buffing anything, you will want to wear a full face shield (not just eye protection) and heavy leather gloves. The gloves protect you from the wheel and related dangers, as well as from heat, as the parts being buffed can really get hot. You shouldn’t wear watches or rings when buffing. Loose clothing should be tucked in or fastened tightly.


The first job I attempted was buffing the brass carburetor overflow tubes. I started with Tripoli Buffing Compound on the spiral sewn wheel. The parts should be buffed on the lower section of the wheel, below the center axis.

    When you buff, you apply various buffing compounds to a wheel that’s spinning rather quickly. Some of those abrasives are going to wind up in the air, on your clothes or on whatever is behind the buffing motor. So, it is a good idea to wear a respirator and a shop apron (or old clothes). I also have a vertical yellow streak on the shop wall behind the buffing wheel. Now I put a big piece of cardboard against the wall. Cardboard is easier and cheaper than painting.

    Now we’re ready to start buffing soft metal. First, check the Motor Wheel Chart that comes with the buffer to select the right buffing wheels and compounds. The chart shows the type of wheel and the correct compound for each step of your project.


Here is a closer look at the top of one tube near the banjo fitting after the first stage of the buffing process, with Tripoli compound, was completed. This tube and banjo used to be so tarnished that they looked black.

    Before doing actual buffing, make some practice passes so you know the best way to hold the part. Examine the part itself. Does it have any sharp edges or areas that will cause the wheel to pull the part out of your hands? Check for any deep scratches in the part. If there are some that are accessible, use a fine file on them. This should be followed by sanding with 220-, 320- and 400-grit sandpaper in the same order. (The Eastwood video shows how an expander wheel tool can be used in place of a file or sandpaper to eliminate deep scratches, but you can’t use an expander wheel on a 3,600-rpm buffing motor.)

    The proper way to buff a piece is to let the wheel run off the edge of the part. You should work on the lower portion of the wheel, just below its center axis. For soft metals, you will begin with a spiral sewn wheel and a compound called Tripoli. Apply the compound to the wheel sparingly. I peeled back the cardboard on the tube and rubbed the compound on the wheel. In the video, the operator takes the compound in his gloved hand and rubs it on the wheel.


Here’s a view of the two tubes with banjo fittings to the right. Here, the upper sides (towards right) of both tubes have  been buffed, but the bottom  sides (towards left) have not been buffed and look black.

    While buffing the piece, avoid using too much pressure. I’m sure I did use a little too much, as I got some black marks where the compound actually burned. Luckily, I was watching and backed off and the marks came off with a soft cloth. Instead of using lots of pressure, be patient and let the wheel do the work for you. Aluminum buffs quickly and will load the wheel fast, so keep watching.

    When stage one is complete, you should let the piece you are buffing cool off. Wipe the piece with a soft cloth. You’ll now be switching to a loose section wheel and white rogue compound. If you have an extra pair of clean, heavy leather gloves, use them. This will keep the new wheel from getting the Tripoli compound on it. Now, repeat the buffing of the part using the loose section wheel and white rogue by moving the part against the wheel.

    If you work slowly and skillfully, you can buff aluminum parts to the point where they have the luster and sheen of a piece of chrome. If you have an opportunity to see Fred Berndt’s Lagonda, you’ll know what I’m talking about. My own S.U. carburetors don’t look quite as nice as Fred’s, but they probably look much better than they did when they left the factory, and I can have fun improving my buffing skills as I play with my new buffing motor. It’s a fascinating tool and when you use it to transform ugly-looking old metal into shiny antique car parts, you get that good feeling that comes from making ancient things look new again.

    There’s one aspect of this job I have to follow up on. Fred Berndt specifically told me he does not clear coat the parts he buffs. The Eastwood video, on the other hand, says that the buffed parts will start oxidizing immediately after you’re finished. It recommends wiping them with lacquer thinner and applying several light coats of clear.

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