1925 Marvel Carb

I have been searching for the brass bowl to fit my 1925 Master Marvel Carburetor.

a 1925 Standard Marvel carburetor was recently up for sale on e-bay, and after comparing photos, I could see the brass bowl casting number 65-10 was common to both Master and Standards. This is not obvious in the Buick parts book because it only lists the complete Bowl Assembly 65-524 Standard, & 65-525 Master. The only Master/Standard difference in the 65- bowl components listed is the High Speed Jet 49-, and the Air vent 111-. So I made the gamble and purchased the e-bay Standard carb, and after it arrived, disassembled the brass bowl. I measured the pin hole at the tip of the High Speed jet by finding a pin that would just fit into the hole, and that was a .040 dia drill bit. It stands to reason the High Speed Jet should be a larger diameter for the Master, and my guess is a simple math ratio of the Master/Standard area of the carb intake should equal the Master/Standard area of the high speed jet. Measure the Carb intake diameter of the Master & Standard, calculate ratio for area of the openings, and it should be pretty close to the actual. Then drill the pin hole out to the larger calculated diameter. The 111- Air valve appears to have been a small spring and a leather flexible seal, both are missing, but should be easy to make. There should be a needle valve that fits into the hole on the top surface of the bowl, but is missing.

this is my theory for the ratios of air intake and high speed jets should be related: I just forgot to measure the intake openings, so didn't include them.

this is the now near complete 1925 master carb-heat riser assembly

the parts book page

Kevin

BCA # 47712

Kevin:

Congratulations on your efforts! I spent quite a bit of time on my carb trying to better its performance. I did post my experiences on it thru the forum a while back. I did buy a new float from Gregg Lange in Mich. What made the greatest difference was carefully refitting the throttle plate to the warped venturi block. Mine was installed incorrectly and left some pretty large gaps. Now I can back out/in the air vane screw a few clicks and tune things very well. I still need to address better sealing of the float needle.

I thought about bidding on that carb so I would have a spare. But by the time I saw it, it was already over my limit.

Keep us posted on your progress.

Larry

Hi Larry

I found your earlier posting on fitting the venturi block and throttle plate. those are good tips - thanks ! now that my carb is nearly complete I can start figuring out how it is supposed to work.

Kevin

You are correct in your thinking about the high speed jet. They will often work a little better if drilled two or three sizes larger to compensate for the alcohol in gas. If you drill too large, then silver solder and drill again. A few years ago I bought three junky marvels on ebay just for parts. I modified my float to get the biggest float I could fit in the carburetor. The needle and seat caused problem and I modified my needle by giving it a viton tip and polishing the seat with valve grinding compound.

there seems to be some very average marvels that show up on Ebay that have been sand blasted within an inch of their life, and if you read the comments on the supplier they are generally bound up tight

On the 33 Marvel, you changed the tips on the stand pipes per application- i.e. going from sea level to a trip to Colorado. You would take your car in and the Buick mechanics would screw on a different jet " tip " Low speed there are none of course. Just the concave area to capture evaporated vodka gas gum.

I don't think NAPA carries them tho.

Kevin,

This page may be of help.

Kevin,

The air valve you refer to has a very special spring inside it. You can see in Bob's carburetor info above that it's weird sort of dual rate spring. Also, what you believe to be a leather plunger is really a brass piston, connected to the flapper by a small rod with a swivel ball joint at the piston end and a small clevis pin at the flapper end.

Also, there is no missing needle valve where you think there should be one. However, I can't remember now what does go there. (I don't have a carb handy at the moment)

The missing needle is called a metering pin.

TWO DIFFERENT ONES WERE USED, DEPENDING ON WHICH BOWL, THE EARLY OR LATE (NOTHING about Marvels is directly interchangeable!)

173-503 was used on the early bowl, but not the later.

173-519 was used on the later bowl, but not the earlier.

There is also a metering pin jet deep in the bowl, a piece of packing, and of course the metering pin link which I believe connected to the linkage on the heat riser.

Jon.

Check back on my posts on my Marvel experience as I have made 3 different metering pin links to find a happy medium on acceleration. Trying to go by the manual that Bob's sells as to the distance the metering pin projects out from the top of the cover. DO NOT USE ALUMINUM! I made one out of aluminum and it bent and it took off revving, I thought I would blow the engine before I shut it off

.Close up of the metering pin link.

I do have a copy of the 1925 Manual for Model "T" type Marvel carbs for both Buick standard and master. If you would like me to send you a copy send me a PM with a mailing address. Very small book but The scans are very big. Or I can resize all and send in an e.mail

It's hard enough on the RHD cars to remove the carby, hate to think how difficult it is for you guys with LHD cars!

Thank you all for the replies.

The data sheet provided by AzBob has solved the High Speed jet nozzle hole size question.

So the metering pin just moves up / down along with the throttle lever ? it appears to be around 3/16 or 1/4 inch diameter, and must have a point at the south end and a clevis cut into the north end for the linkage ? The small clip on the top corner of the bowl is the retainer for the metering pin packing ?

Kevin

Kevin,

Here is a photo of the metering pin out of my 1926 Marvel T-3. The small clip on the top corner of the bowl is for the pin packing. The main body of the pin is .216" diameter and the metering end is .100" diameter. Yours may differ somewhat.

AzBob,

Do you have the page on the carb information for a 1923 Buick 6 cyl roadster convertible? if so, would you be so kind as to post it. Thanks

Paul S Searcy

pssmls,

That particular manual only covered 1925-30.

I have a partial carb given to me by Oregon Desert 45. I have been trying to save some of the internals. I had sent him a PM about de-rusting by Electrolysis. He asked what I was using.. Hence this response..

An old battery charger, a non conductive container.(a 1 gallon milk jug worked)

but I have some Tupperware containers that I use. "Washing Soda" found at the grocery store. A sacrificial piece of steel.

Google "Rust removal by electrolysis" and you should find many explanations, recipes etc. I collected antique carpenter tools and I have used this method successfully to remove rust from old planes hand saw blades and such. So I thought I would try it on the carb. But of course with a combination of iron, brass and the die cast composition results so far are disappointing. The air vane plunger being the most problematic since it has swollen in the brass barrel. I still have hopes to get most of the air vane out. Most of the venturi block came out last night. The die-cast material "creeps" and grows into the rusted cast iron. Please note the safety procedures and precautions as you are dealing with water/electricity and toxic explosive vapors.

I will post on the forum since the PM will not let me upload a photo.

Best regards and be careful!!!

Larry

Kevin:

I had some success tonight. I saved most of the internals, at least enough to make up some patterns. (Venturi block is pretty rough) The pin holding the link from the plunger to the air vane was the toughest to get apart. The plunger was full of sludge. I set the brass barrel in the 3 jaw chuck on the lathe then drilled and tapped the end of the plunger starting with a 4-40 then kept working up to 10-32. I was finally able to get a good bearing to be able to use a 3 1/4" 10-32 screw to use as a puller. Even drilled out the broken screw out of the casting and save that thread! (Where the jet section bottom plate attaches.) Of course the spring was toast. If I am ever able to re-use this cast iron section I will use a cylinder hone to clean up the inside bore. I just wanted to prove that I could do it.

Thanks again for the cold weather diversion.

I noticed the air vane in my carb was not closing completely, but had a gap around 1/8 inch to the wall even with the brass barreled damper pot screwed in as far as it could go. The air vane was hitting the Venturi block just below the hinge pin.

The brass hinge pivot pin was easy to remove, but the small pin linking plunger to the air vane was very difficult to get out. After the air vane came out, I used a hand file to remove material from the area that was binding. Either the venturi block or air vane or both must have swelled up enough to cause this. I tried a second time to remove one of the 2 screws holding venturi block in, and for the second time broke the screw driver bit. It can remain in place for now... I can reach in with sandpaper to clean out the rust and carbon build up.

below photo - area that I removed material with a hand file shows up as a white line along lower edge of air vane

after a few iterations of filing and fit checking, the air vane moves easily and closes completely.

Since that small pin connecting plunger to the air vane was so difficult to remove, and I don't want to risk breaking the lug off as Larry experienced, I should make a straight pin and cross drill it for a small wire.

Kevin

BCA # 47712

Although your carb looks slightly different than my 1924 version, I believe that you never had to remove the pin connecting the plunger to the air vane. If you remove the damper pot, it allows enough slop so that the plunger can just slip out when you extract the air vane. If this is true for your carb, as it was for mine, you can reinstall a pin external to the carb assembly then just slip it all back in place.

I have had my carb apart many times and have never removed that pin.

This carburetor is on eBay now and is for a 1925 master. It has the casting n0 10-87 on the cast iron portion that shows in the last picture. This is the same as mine which I obtained years ago off of a 25-40. It looks like it may be good for parts although it is missing the metering rod. Leon

http://www.ebay.com/itm/Vintage-Early-Marvel-65-10-L-Brass-Carburetor-Fits-1923-1924-1925-Buick-1921-Pat-/111618485207

Leon:

Thanks for posting. I guess I will try on it for the fellow who we worked on his fathers 1925-45. The carb was a pretty cobbled up mess. More work....

Larry

Larry, did you buy the carb? Leon

Leon:

I did get the Marvel carb. I don't know the internal condition until I receive it. I will see if I can get it serviceable for the fellow nearby.

After soaking in solvent for a week I finally started to disassemble the carb. Only broke one screw in the brass bowl. I was able to drill it out. The rest came apart easily and will clean up well. Dash pot, plunger, spring, venturi block all in good shape. The metering pin and rod link were missing.

This is an old posting, but I wanted to interject.  The biggest problem with pot metal growth in these Marvels is with the Venturi.  The half circle looking part with the hole in it.  The air vane that pivots is rarely the problem.  The interference of the 2 parts from pot metal growth prevents the air vane from laying smooth against the carburetor bore.   There are always exceptions but in the half dozen 1925 Marvel carburetors that I have worked on, removing the venture and filing the surface flat again, or replacing the venturi fixes the interference problem.  I have not needed to remove the air valve piece that pivots or make any modifications to it.  

- It is best to use a new 5/16" tip screwdriver with a square shank to remove the 2 venturi screws.  If you break a screwdriver doing this, buy a better one.  Worst case, drill out the screw heads.

- Carburetor venturi's are available in aluminum from Tony Bult or Roger McGinnis and this is a better option than filing the venturi face flat again and reusing the pot metal.  

- There is an entire write up on rebuilding these carburetors on this forum.

Hugh        

Having had the carb on my 25 standard tourer off the car a dozen times with original float (dries and resealed) I was still having mixture problems..until I used Teflon tape on the main adjuster brass piece. I also found an original spring under the front seat!

The old spring had been stretched. Vola! She's running great now with just a little choke. I also drilled main jet to 1.5mm..might try 1.6mm next.  

Attached is a link to rebuilding your Marvel carburetor.  There are several new parts available to bring it back to specifications.  The metering pin jet for a 1925 Standard should have a 51 stamped on it.  The high speed jet is a 57.  I would have to get a wire set to measure the bore size of these jets.  The main jet is the jet with the mixture needle up the bottom.  None of these jets should require drilling.  The air valve adjuster for the marvel spring barrel should not require teflon tape.  You might want to verify that you have the correct spring as there are several that look the same but have different spring rates.  1925 Standard is a 1 year only spring.  There is information on the forum regarding the spring and replacements.  You should not have to run a little choke and I am not advocating that going up another drill size is the answer.        

I think if I get a new float and spring I should be good. The teflon tape definitely made a big difference as was sucking air through there. Cheers Herbert.