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1928 Std 6 replacement carbrueter


humber349

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There are a number of different S.A.E. size 2 carburetors which will run the engine; most of them superior to the Marvel.

The problem is adapting any carburetor to replace the Marvel with the odd size and configuration flange used by Marvel. An adapter must be machined to do so.

Jon.

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This was previously published in the PWD Newsletter:

One of the most condemned and abused components in Buicks from the teens to the early thirties is the infamous Marvel Carburetor. Many Buick owners have plugged their exhaust heat systems and either replaced their original Marvel Carburetor with a Zenith, Carter BB1, or some other updraft carburetor. Some just gave up and flipped their intake manifold to install a more fuel efficient downdraft carburetor to improve both performance and mileage in their cars.

I still run original Marvel carbs in most of my Buicks. I use full choke from a cold start & usually need to keep the choke out 1/3 to 1/2 until the engine warms up. This seems to be normal for Buicks with or without working exhaust heat systems. Mileage & performance is not as good as downdraft carburetors, but I believe that keeping these old girls going with their original equipment is part of the pleasure in driving and maintaining these old cars.

The most common cause of Marvel carburetor problems seems to be the need to replace the 70-80 year old cork float. I know that many prewar Buick owners will struggle to get their Marvel carburetor to work properly with these old dried up cork floats. It would be rare for such old cork floats to work reliably, so they must be either be replaced or coated to prevent saturation. The purpose of the float is not just to start and stop fuel flow to the engine; it also continuously maintains the correct fuel level at the jets. The jets are carefully sized to atomize and supply the correct volume fuel & air to the engine at all operating speeds. If the fuel level is too high or too low, the jets will either starve or flood the engine. Sound familiar?

I have several old books and manuals that troubleshoot and/or explain the various designs and theories of how all kinds carburetors work. I also have Harold Sharon’s book “Understanding Your Brass Car” that explains how any do-it-yourself amateur can replace the cork in an updraft carburetor to drastically improve performance. Harold explains in simple terms how you can use “Crazy Glue” & wine corks to make a replacement cork float to fit in almost any carburetor. He also states that coating the cork is not necessary. I expect that gasoline additives & ethanol in modern gasoline would probably dissolve any of the old recommended shellac coatings and gum up everything anyway. But, I know that model airplane dope or Crazy Glue can be used to seal cork floats.

Another relatively common problem with Marvel Carburetors is with the main jets that develop small cracks. These cracks can easily be soldered to solve the problem. Just run a drill bit with the same inside diameter through the jet after soldering to make sure excess solder does not restrict flow.

The ultimate alternative is to flip the intake manifold and bolt on a Rochester carb from a "stovebolt six" GM engine with similar displacement. There are several models of this carb...with and without automatic choke. My son is considering doing this on his 29 Buick. If you keep all the original parts, this modification can easily be reversed if you or the next owner prefers to show the car.

Edited by Mark Shaw (see edit history)
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