1931 marvel carb service info

[TTracing]

Does anyone have a service (I will not call it a book lol) sheet for the 1931 marvel.

 

I searched online and found a 26 -1930 and bought that and the 1930 is similar but not quite the same and I am having issues getting this on to start easy and run right.

 

been all thru it 2 times all looks ok but the air valve adjuster is different than the 1930 and I am unsure of 

proper spring length and initial adjustment

 

Any help would be appreciated

 

Bill in NJ

[TTracing]

Finally found the 1931 supplement to the marvel carb section for Pontiac 6 all it says is here are corrections to the 1930 specs no mention of 1931

[Hans1]

The air valve has two surfaces.  one is the large pivoting blade. The other a short raised ridge is at base of air valve, at pivot area 90 degrees from large blade.  Polish the brass pin and hole in air valve. 

When the large  blade is vertical, the little raised ridge is to have 5 thousands clearance to the idle jet venturi housing, shaped like a semi circle.

The Idle jet venturi housing is removeable via two countersunk screws.

My experience is that the flat side of the semicircle venturi housing is often expanded at the pointed ends.

I use fine sand paper on a flat surface to remove the growth and realign the venturi housing clearance to the air valve.

 

The info in my book indicates the calibrated spring is 1  1/2 inch long.

 

The operating process is to start with brass knob even with end of the ratchet and to adjust in or out from that position, based on a fully warmed engine.  

 

On your '31 carb what is the  10-XXX number on side of air housing?

[TTracing]

Hans Thanks for the reply that is more info than I had I just went and looked and I didn't see any stamped numbers.  the tune up sheet I have says I should have a 955 where on the air housing should the number be ?

 

I did find some where the part about   start with brass knob even with end of the ratchet  which I have done and at idle it seems a bit better about 3/4 of a turn in hot.

 

Just yesterday I finished up a new timing chain and reset timing and it started nice and easy Idle was good and it seemed to run Fine for 10 blocks even pulled up an fair hill in second and went several blocks at 30 mph all good thought all was good then about 2 more blocks and no high speed it just dies then you can restart and it will idle but that is it.    

 

I did polish the bore and piston and pin last time I pulled it apart but that didn't seem to help  Sounds like I need to check that clearance and the hole in the air valve

 

thanks again for the reply

Bill

Edited July 6, 2023 by TTracing
correction (see edit history)

[TTracing]

Hans

 

Had a little more time today and pulled the carb again   and I just couldn't see the numbers in the car.....    It's a 10-228   not what my sheet calls for I have not had a chance to try and see what is for.

 

The only other thing is noticed was the the edge of the air valve is very sharp

 

Bill

[carbking]

Bill - Marvel did everything in their power to make it difficult for aftermarket suppliers to supply parts for their stuff.

 

This included often the use of TWO DIFFERENT numbers stamped on different examples of the same carburetor depending on if the carburetor were purchased with/without a heat  riser. On some carburetors, Marvel did NOT stamp the identification number at all.

 

Decades ago, I went through the Marvel factory books (dozens of them) and produced a listing of casting numbers / identification numbers. Many are not unique, but the 10-228 IS unique to the 10-955 carburetor used on 1931 Pontiac, and 1931 G.M.C. with Pontiac engines.

 

Here is a link to that list:

 

Marvel casting number cross-reference

 

Jon

[TTracing]

Jon

 

Thanks for the reply 10-228 is definitely a raised casting number.   Seems I at least have the correct Carb.   

 

Well after going thru my recently received 1931-1932 Oakland Pontiac shop manual  which is actually a 1930 with 31 and 32 supplements

 

It seems the air valve spring length was stated in the 1930 manual as 1 1/2 inches however the 1931 supplement shows a correction to 1 1/16.

My spring is 1 1/8 sort of close and appears to be in OK shape. 

 

As for the gap between the Idle venturi and the lip on the Air valve I have more like .010 thousands not sure if that is a problem.

 

So far I don't see anything to cause the issue I have ......

 

 

Edited July 7, 2023 by TTracing (see edit history)

[32Pontiac6]

My website has a Marvel Carburetor repair manual and Calibration specifications for each year Pontiac with the Marvel Carb.

 

https://pontiacsplithead.com/misc-reference/

 

[carbking]

Not difficult to understand the air valve spring length issue.

 

Most Marvel air valve springs have a free length of 1 1/2 inches, including Pontiacs in 1928 and 1929.

 

The 1930, 1931, and 1932 Pontiacs use the shorter spring.

 

Jon

[TTracing]

Ok Folks  

 

Just a follow up problem is fixed after have the carb apart 4 times and not really finding anything of substance.  Decided to look else where    Since I had already tried a different coil and all the parts in the distributor were new. wasn't sure what to try next so I replaced the easiest one first and replaced the new condenser with a NOS one from 40 years ago when I had a 64 Falcon Convertible.   And that was it car now runs great.   In case some have not read previous posts  problem was always started great and idle was fine and cold it drove good as soon as it got hot no high speed eng would not rev up at all.

 

Thanks again to those that replied

Bill