Marvel Carburetor Disection

[Y-Blockhead]

Does the GAV act the same way in the Marvel Schebler as in the Zenith?
How much do you open it at start, and how much in normal running?

Herb Concord, I think you answered this question - thanks.

Yes Herb is correct.

One thing to remember is on the Marvel when tuning is the idle mixture screw controls the gas flow so when you turn the screw in, it leans the idle mixture, out enrichens. Opposite of the Zenith and Tilloton.

 

[EZLIFE]

I have found this idle jet is threaded into the lower body with a 10-32 thread. It is a thick walled tube so you can get a firm hold on it and it will come out. Don't know how they set the height of them but I would measure them before removing and reset again with some thread locker.

Has anyone confirmed if the idle jet is threaded? Or pressed in?

 

[Herb Concord Ca]

Yes, the idle jet, (long tube) is threaded. Like gmcpaso says, measure the height before you remove it.

 

[jeepguy1948]

Dumb me, I did not know that the Zenith idle adjustment screw was an air adjustment not a fuel adjustment! I have a Marvel that I just bought on it’s way and some parts from Renner so I’m sure that this thread will prove helpful.

 

[jeepguy1948]

Would someone explain to me the use and adjustment of the power needle? Obviously it can’t be adjusted while driving.

 

[Joe K]

Would someone explain to me the use and adjustment of the power needle? Obviously it can’t be adjusted while driving.

Look back at post https://www.fordbarn.com/forum/showpost.php?p=892414&postcount=23 particularly Photo 9 which is the schematic of the Marvel.

On the schematic note the comment:

Note: when using the explanation from the Service Manual, the combination of the GAV and fixed orifice should be considered the equivalent of the Power Adjusting Needle and seat.

The pix 8 in the same article shows the Power Adjusting Needle (and seat) but this is taken from the "Tractor" variant of the Marvel Carb. The Power Adjusting Needle and role are taken by the GAV in the Model A application.

So I expect you'll use the Power Adjusting Needle similarly, but perhaps less conveniently (i.e. 3/4 or a turn open to start, perhaps 1/4 open when warm.)

Pretty much a "start-up" function for an industrial engine. Model A users are more discriminating to the operation of their engine.

Hope this helps.

Joe K

 

[RENNERS CORNER]

I make or have every part for the Ford released Marvel Schebler.

These actually have a Ford part number they were released by Ford motor company in 1948 as a service replacement to be installed by the dealers.

They were a simple alternative to the Zenith, they're only downfall is warping but that can be easily fixed with a file.

 

[RENNERS CORNER]

Float / fuel level = 3/4" below the gasket line.

 

[mcgarrett]

Nice work! I'm restoring 10 of these carbs now as we speak and really enjoying the process. Thanks for posting all the important info and tips. Just for starters, getting them apart without damaging any of the components can be a real challenge. Some parts for these carbs are more expensive than Zeniths, like the GAV and choke driver, but in the long run I've found they outperform the Zenith by a long shot.

I've also modified the Zenith GAV to work in the place of the more expensive Marvel hex type GAV and choke driver and have one on my '30 Roadster now that performs perfectly.

 

[41blueoval]

I have one of these carbs on my 31 A that will not idle or rev up without the choke partially on. The mount flange was severely warped, which I fixed. Is there other areas that have a warp issue? This carb is remarkably clean inside. Does anyone know what size the idle jet orfice hole should be?

 

[Y-Blockhead]

I have one of these carbs on my 31 A that will not idle or rev up without the choke partially on. The mount flange was severely warped, which I fixed. Is there other areas that have a warp issue? This carb is remarkably clean inside. Does anyone know what size the idle jet orfice hole should be?

One thing to remember with Marvel Carburetors is the idle mixture screw operates opposite a Zenith. The idle screw on a marvel controls the amount of gas not air like a Zenith.

So turning the idle mixture out will (counter clockwise) will enrichen the idle mixture. If you turn it inyou will be leaning out the idle mixture.

The top easily gets warped if the 4 screws are over tightened. I tighten the screws only enough the colapse the split washers.

 

[41blueoval]

Problem solved pm, entire bowl vent passage was plugged. M

 

[old31]

Nice work! I'm restoring 10 of these carbs now as we speak and really enjoying the process. Thanks for posting all the important info and tips. Just for starters, getting them apart without damaging any of the components can be a real challenge. Some parts for these carbs are more expensive than Zeniths, like the GAV and choke driver, but in the long run I've found they outperform the Zenith by a long shot.

I've also modified the Zenith GAV to work in the place of the more expensive Marvel hex type GAV and choke driver and have one on my '30 Roadster now that performs perfectly.

Could you talk about the conversion or have any photos of how you did the GAV conversion.

 

[mcgarrett]

old31,
I can take some pictures of the modification and post them later this evening when I get home along with a description of how I did it.

 

[Y-Blockhead]

Problem solved pm, entire bowl vent passage was plugged. M

That would certainly do it. Good job and thanks for sharing your outcome.

 

[mcgarrett]

old31,
As promised, here is the GAV conversion info you asked about...

Some of the Marvels I was rebuilding did not have a GAV needle housing & needle or a choke driver. A Zenith GAV needle housing is pipe thread and the Marvel is straight thread, so they won't interchange. Marvel replacement parts are unique to that carb and some are a little pricey, so I decided to try to adapt a Zenith choke driver, GAV and needle to see if it would work.

I used a Zenith GAV needle housing (barrel) and very carefully sanded down the hex flats and threads on a tabletop belt sander with a 1" fine grit belt until the hex and threads were gone and the barrel was smooth, round, and uniform down its length. I then took one of the Marvel GAV needle housing nuts and drilled it to the same diameter as the Zenith GAV needle housing (11/32" is a good fit). I fluxed the barrel with a small propane torch and slid the newly drilled nut onto the needle housing (barrel). I slid the nut fore and aft on the barrel until it was pretty close to the same basic location allowing for adjustment travel using another Marvel needle and nut that I had on hand to compare with and then applied some solder to the barrel end opposite the nut threads. The last step was to break off the brass housing "fingers" down near the tip of the needle to allow for clearance down in the needle hole. It was trial and error until I arrived at the correct location of the nut, but it worked nonetheless and I saved a fair amount of $$ for a few minutes work. Here's the finished product...

 

[old31]

MC nice job, I like it. Smart.

 

[wadeyboy]

well just what i needed and finally identified my carburettor.

 

[wadeyboy]

its great to know what carb i have on my tudor

it has been off road for a few years and i did clean and inspect carb recently

today when i tried starting i had fuel squirting out the float vent hole.I wonder did i hod choke out to long? or do I have anorther problem?

suggestions please

 

[Aretino]

Great work. I purchased a Marvel from Jim Bullock several years ago and it improved my cars performance. I purchased a second Marvel as a spare and will be cleaning that carburetor up soon. Your post will be of great help.