1932 series 50 carb problems

[simhin]

hello,

I have a series 50 that has had head problems....this is now repaired, and we've got carb problems...does anyone have any info on the marvel Scheibler carb? Set uop and operation.

Any guidance, gratefully received. (the car hasnt run for 50 years)

[michaelod]

Not sure how similar the 1932 carb is to that used in the 1929 but this brochure for the Marvel found on the 1929 Buick website might help:

www.1929buick.com Photos :: 1929 Marvel Carb

Thanks,

[Mark Shaw]

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 Carburetor 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[color=#262626

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 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 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.

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 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.

Edited October 11, 2011 by Mark Shaw (see edit history)

[simhin]

Amazing replies thank you both!....that gives us a lot to go on with

Simon

[simhin]

Gentlemen......the beast lives.

Today the car moved under its own steam for the first time since my father bought it in 1962! Admittedly it was only 20 feet back into the garage but its still a good result.

Tomorrow we drive it for a short speel to find out what else needs doing.

I have a question on oil pressure, we fixed up a new guage to eliminate the possibility of a duff original, and it shows 30 psi when cold, going down to 20 when warm. Does that sound correct?

Once again i would be grateful for any info

Cheers

Simon

[Mark Shaw]

Simon,

Yup, your oil pressure may go even lower when she really warms up....

What did you find wrong with the carb?

[Bob Engle]

A caution on the oil lines on 32 Buicks. Many oil filters have been changed out to cannister filters and the exit line to the cylinderhead has been increased in size from the original. This will allow too much flow to the rocker arms and decrease the oil pressure to the rods and mains. The inlet line to the filter should be 1/4 " brass tube and the outlet line to the cylinder head should be 1/8" brass tube, same as the line to the oil pressure gauge. If you have copper the lines have been changed.

Bob

[simhin]

Mark,

The carb was just old, dry and dirty. We fitted an electric fuel pump from a different vehicle and we think the problem was mainly float related. Its not cured yet, it got through 3 US gallons of fuel in 90 minutes on little more than tick over!!

But at least the car was running enough for us to check out the oil lines and water lines, and the head repair, which was the main thing. We are going to try to remake the float, so it can be used a little to shake down everything else, then I'll try to get a carb repair kit over from the States.

Cheers

Simon

[Mark Shaw]

Simon,

You can use Krazy Glue to make three wine corks into a new cork float. I coat mine with Krazy Glue to seal them too.... Works great!

[simhin]

Mark,

We are improving, but the carburation is still not correct. Any more clues to setting it up?

Simon

[carbking]

Simon - a few things to look at:

(1) the airvalve MUST completely close. Often, the "spacer block" (low speed venturi) which is made of zinc alloy (pot metal) "grows". When this happens, the lower edge of the airvalve binds against the spacer block and the airvalve will not completely close. This issue may be resolved by removing the spacer block(s) and sanding the flat side on a piece of glass using 1200 grit emery paper. Repeat. The airvalve MUST close completely.

(2) an electric fuel pump is going to overpower the float (even if you have one of the aftermarket brass floats) unless you regulate the pressure to about 1~1.5 psi. The mechanical advantage and buoyancy of the float are insufficient to hold more pressure.

(3) try to test the heat riser for leaks. Not sure of a good test without removing the whole thing, but perhaps you can remove the carb and blow compressed air into the exhaust, and see if it comes out the intake for the carburetor. The heat riser has a pressed steel insert that is surrounded by exhaust. The intake air/fuel mix passes through the insert. If the insert has a rust hole (COMMON), the engine acts like a modern engine with a defective EGR valve.

Jon.

[simhin]

Thanks for that...should get time tomorrow to try some of your tips

simon