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1925 Buick Master six convertible

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good day all i have just bought a 25 Buick master six that has been in two collections for 60 plus years having some problems with the marvel carb wanting to overflow. i have changed the float over to plastic the seat and needle valve look like new so dose the carb she will run but not very well all of the linkage is I would say perfect with the heater parts are hard to find for the 25 master oh also the clutch is stuck 

any advise would be great before frustration sinks in and she will have a new home 

Thank you  

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  • I suggest you first make a "clutch depressor".  Make a stick that will hold the clutch fully depressed when it is parked for more than a day or two.  
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    Marvel Carburetors

    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 Carburetors 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 older they are the more simple they are... If you have Marvel carb issues, first 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 or verify that it is original. If it is a straight spring, it may be 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 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 struggle to get their Marvel Carburetors 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 & 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 fuel to supply the correct volume of fuel & air to the engine at all operating speeds. If the air control knob is not properly adjusted or 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 from modern gasolines.

    Another potential problem with Marvel Carburetors is with the brass jets that sometimes develop small cracks. Plug one end of the jet with your finger and suck or blow to determine if there are 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 carburetor from a "Stovebolt Six" GM engine. There are several models of this carburetor 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.

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     Welcome,  Attached are 3 links for your review.  Lots of information here if you do a search.  Please attach some pictures of your car.  Hugh









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  • 2 weeks later...

I had a frozen clutch in my 29-44 this spring, due to a very damp garage this past winter.


Here's what we did:  I tried driving it up and down a quiet road, with the clutch depressed, hitting the brakes occasionally.  This didn’t work so I tried lifting the back wheels off the ground and running the car while occasionally applying the brakes hard. (I did NOT do the next step suggested by several people which was, jack the back wheels up and drop it while running, due to possibly breaking an axle.)  Next, I removed the floorboards to get at the clutch inspection plate on the transmission.  I sprayed brake cleaner onto the clutch plates, several times a day, for a few days and then run the car for an hour or so to warm up the transmission (I also used my wife’s hair dryer, on high through the inspection opening, to add extra heat on the clutch.)  Then I drove the car occasionally applying the brakes and the clutch broke free.  I guess, If all these don’t work, then it’s time to pull the transmission.  One way to avoid this, is to cut a board long enough to fit between the depressed clutch and the front seat and leave it in position for the winter.  This will prevent the plates rusting together.


Bill McLaughlin

1929 Silver Anniversary Buick Club

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Bill's description made me think about your situation a little.  1925 was the last year for the "open" style of multi disc clutch shown below.  This is a photo looking up at the clutch with the lower clutch cover removed. 

It takes very little effort to remove this lower cover.  This gives you a good view of all the clutch plates.   Use a rubber mallet or pieces of wood and gently tap on the plates to loosen them.  Transmission in neutral and rotate the engine with the hand crank.  Work both sides.  Do this outside.  Stay to the side, tap on the sides and let any dust fall to the middle.  Tap on the steel part of the clutch disc that is outside the diameter of the friction discs.  Wear an N95 dust mask.  I would not suggest breathing any of the dust that comes off.  Use a shop fan and stay up stream.  You may also be able to access from the top side, but you have to remove the floorboards, and the access hole is much smaller.  Use a piece of 1 x 2 to the seat frame to depress the clutch.    Hugh




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