How to rebuild a 26 Buick Carb

[Guest 97welter]

I have a 26 Buick Standard. How hard is it to rebuild the carb? I have done a couple for my 50 Chevys. Is the updraft carb more difficult than the downdraft carbs? Who has a kit available?

[Mark Shaw]

The older they are the more simple they are... Just give it a good cleaning and check the cork float. Replace it if needed and set the fuel level just below the top of the lower jet. Make sure the air spring (inside the big adjustment knob) has a bulge in the middle. If it is a straight spring, it is the wrong spring.

Set the big knob even with the tang and open the bottom fuel screw about 1 1/2 turns to start. It should start and idle with these settings....

The Marvelous Marvel Updraft Carburetor

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. 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 November 19, 2010 by Mark Shaw (see edit history)

[Guest 97welter]

So, if you flipped the manifold and put a 50's Chevy carb on, what would you use for a fuel pump? Do you still use the vacuum tank?

[Mark Shaw]

No, because the vacuum tank simply drains via gravity to the original updraft carburator. Flipping the manifold puts the carburator too high for this to work. You would need a fuel pump to make a downdraft carburator work.

[Raycycled]

Hi there what is the high speed jet size suppose to be I can’t get my 27 Buick to run right with out having the choke out . Ray 

[Guest]

48 minutes ago, Raycycled said:

Hi there what is the high speed jet size suppose to be I can’t get my 27 Buick to run right with out having the choke out . Ray 

Welcome.  It would be better for both if you had started your own topic.

That aside usually id the choke needs to be out to keep running it means the idle jet is plugged.  Unscrew it and look through it.  A plug or partial plug is obvious.  Blow the plugout.  Don't use a mechanical means.  You might enlarge the jet.

Good luck with your carb.

 

[Hubert_25-25]

There is a procedure in this link if you want to go thru the Marvel carburetor yourself.   I would not abandon your Marvel carburetor.  They just need to be set up correctly.  There is a lot that can happen to it after 90 years.  Also information on blanking off the heat riser system.   Hugh

 

Edited April 22, 2019 by Hubert_25-25 (see edit history)