VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Correct carb on '40 Special Deluxe

I bought a carburetor from another member last winter and installed it today. What a difference. I had taken the original off for a rebuild and the pivot was worn for the accelerator pump so I had put on a W-1 off a '48. I ran ok but was never 100%. The correct carb works trouble free. What is the difference with the '48 W-1? Thanks, Don

"I had taken the original off for a rebuild and the pivot was worn for the accelerator pump so I had put on a W-1 off a '48."

Don,

I have a '39-'40 carb on my '36 PU. Both the accelerator pump bellcrank bore and the throttle shaft bores were worn egg shaped. The fix was putting bronze bushings in both bores.

The challenge was making a guide pin gripped in the milling machine drill chuck (a drill press would also work) to precisely align the float bowl cover so the oversize hole is correctly centered.

If you'd like to see that setup I could email you a photo if you give me your email address. Mine is raywaldbaum@gmail.com.

Those bushings take all the slop out. A side benefit is vastly improved idle quality with air leakage along the throttle shaft eliminated.

Still wondering what the differences are between a '40 W-1 and a 48 W-1. thanks

This is where I went to identify my carbs. Carter W-1s

"Still wondering what the differences are between a '40 W-1 and a 48 W-1. thanks"

Round accel pump shaft w/easily replaceable leather vs flat shaft w/ difficult to replace leather. Float bowl cover w/bore for accel pump bellcrank shaft vs float bowl cover w/permanent stud for bellcrank to pivot on.

Oops, forgot to mention different main jets and metering rods. But the rods and jets are interchangable to get the perfect jetting combo.

On my '36 engine I have a '39-'40 carb with a '37 main jet and a 1-step lean '37-'38 metering rod with the tip diameter reduced from 0.047" to 0.0445". Calculating effective main jet open areas with different jet orifices and metering rod diameters, trial and error and detailed notes of what works and what doesn't in all the throttle positions from cruise through WOT zeros in on the perfect combination. It runs great with that combination I found. You can do it too.

Changes made to 1941 carburetor.

Refinements in the 1941 carburetor contribute to the improved fuel economy and performance of the more powerful engine. The throttle bore diameter which was 1 7/16", is made oversized to 1 1/2" to improve air flow conditions, which results in more power and better fuel economy.
To eleminate stalling of the engine when making a very quick stop the idle tube is redsigned with the orface placed lower. In addition, the orface is located vertically in the tube to miniamise the possibilty of dirt obstructing the opening.
The balance passage between the air horn and the float chamber is changed to permit freerer flow of gas vapors from the float chambers. In making the passage more direct, construction also is simplified. The air horn end of this passage now terminates in a tube that is located on the atmospheric side of the choke valve. This eleminates the hole in the choke valve shaft that was used in 1940 to allow air to enter the balance passage when the choke was closed.
The choke valve is now an angle valve, which eleminates the retractor spring on the lever.
This unobstructed balance passage for vapors also allows the use offff a metal metering rod hole coover, which replaces the bakelite type.
The accelerator pump lever and its mounting is revised to increase the life of the bearing.

The 1941-1948 W-1 was improved and did increase the fuel milage of the 1941 car.
Farther improvements made in the one year only 1949 w-1 eleminated some of the previous problems + it had the automatic fast idle link to increase idle speed when the choke was used.

The replacemen 569S carb. is the desireable replacement for the 1932-1936 versions of the W-1.It is the same as a 1941-1948 carb. other than the accele. lever.
The 1940 had a 94 thousands main jet, the 1941 a 93.
The 1940 metering rod was 67-40 ' metering rod and the 1941 a 67-46.

So if a '41 or newer W-1 is used on a '40 should the metering rods be changed to the '40 specs? Just curious, the car runs way better with the earlier carb than it did with the newer carb.

I would not change anything if the car runs OK as is. In changing metering rods the main jet shoud be changed also.

"So if a '41 or newer W-1 is used on a '40 should the metering rods be changed to the '40 specs? Just curious, the car runs way better with the earlier carb than it did with the newer carb."

Don,

The choice is whether you want the vehicle to run "OK" as Gene mentions or whether you want to optimize the carburetor to allow the engine to run at it's "Best". It's "OK" vs "Best".

I encountered the same situation that you are experiencing when I adapted on a later model carb to solve the problems inherent in the 2-screw air horn and 2-screw float bowl carb. At first the later model carb ran much worse. Ovbviously gas and air were not being blended in the proper quantities to meet the engine's needs.

Carburetors are inanimate objects. The choice we have is whether to be helpless and accept "OK" or learn about how carburetors work and do some experimentation to find "Best". I personally choose to not be outsmarted by an inanimate object. There are excellent books on this subject like Doug Roe's treatise on Rochester carbs. If you know how something works you can make it work even better.

I have read on this forum that the jets and rods are not interchangable between carbs. That is absolutely NOT correct. They are all interchangable between W-1 carbs and your perfect match of main jet orifice size and metering rod diameters exists. The challenge is to find it. Those parts are all out there. If searching for them is not your thing they can be made. The jet is just a threaded brass bar with a specific entry shape and orifice size. The exact orifice sizes can be created with jet reamers. Metering rods can be made from brazing rods.

Tiny variations in size of a thousandth of an inch and less make the differnce between "OK" running and "Best" running. It's an interesting and rewarding quest.

May I ask another question?
Is it true that the Carter W 1 was the standard carburetor and used in many different cars?
My carburetor in my car (1940 special deluxe) is maybe from a later 235 engine and I guess not the right one for my 216 engine. Runs too rich and needs too much gas. As well the metering rod needle was never used in chevrolet cars. Could not find the stamped number in any parts book.
So I do experiments too. For sure the car runs, but it could run better I guess. If I take the spark plugs out they are always deep black. Clear sign for a too rich mixture.

Dir try to find needles and seats at ebay.

Regards
Stefan germany

The last Carter w-1 was used on the 1949 Chevrolet engines. From 1941-1949 the 235 was installed in large trucks and used the same carb. as a 216. In 1950 the 235 was "hopped-up" a little and the car and trck with a 235 engine had a larger 1 9/16" throat on the new Rochester carb. and the stud spacing was wider so a W-1 will not interchange.
Carter sold various versions to many car makers and some were equipped with an automatic choke.
Running rich could be caused by other things including the float level set too high or the metering rod out of sync. with the throttle opening.
The are numbers stamped on the main jet aand the metering rod that would be able to ID what is causing the problem if it is in the fuel metering system.
or you get get a main jet and metering rod for a 1940 W-1.

Stefan,

I have an extra NOS Carter needle & seat that is original equipment on 1929-49 Chevy. It is Carter part number 25-33S, a relatively rare part because it was used only by Chevy and Studebaker. It is all metal so is not adversely affected by present gasoline formulations.

As Gene points out your rich running condition can be due to a number of causes. If I were in your shoes I would first replace the needle and seat, set the float level to the correct position for your carburetor model, verify that you have the original main jet and metering rod for your carburetor model and year car and synchronize the metering rod to the throttle position with the gauge (pointed rod) made for that purpose.

Spark plug color can be misleading concerning air/fuel ratio if the plugs are of an incorrect heat range, if the spark is weak and/or if timing (initial, centrifugal and/or vacuum)is incorrect. I have AC 46 plugs in my '36 Chevy and I'd be glad to send you a picture of what they look like with a correctly jetted carburetor. Those and similar heat range plugs are abundant and inexpensive on ebay if you're not impatient.

I have 4 carbureted vehicles and they all responded to careful rejetting with increased power, improved fuel efficiency and cooler running. The gasoline of today is not what it was when some of those carburetors were made 70 - 80 years ago so some carburetor tweaks can be very helpful.

If you're interested in the needle/seat and/or the metering rod gauge dimensions so you can make one my email is raywaldbaum@gmail.com.

Carburetor jetting is not rocket science but does involve some trial and error, patience and good record keeping.

hello brino, hello Don,

thanks for much input, must read and understand it when I am not in hurry to go to work as I am presently. Must leave soon.
Short answer: I found parts at a ebay pal named iceracer1995. He sells NOS carburetor parts.
With my carb I made a complete overhaul last year including all adjustments, but as long I still have a wrong jet and metering rod I cannot reach the right performance. So now I have to wait until the letter with the parts passes the german customs.
Later I will let you know about my carburetor experiments.

To understand better, how the carter W1 should work, there is still an unanswered question. The metering rod is thin at the bottom and has more diameter until it ends at the eye on top. I know, "cone" is the wrong word, but it says how that rod is formed. Thin at the lower end, thicker at upper end.
If the carb is in idle position, should the met. rod needle close the main jet seat completly and the engine is feeded only by the gas passing the idle adjustment needle?
I remember, one of my pals owning another of these in germany very rare 1940 chevies (only 4 known), told me, he can close the idle needle to zero and the engine does not stop running. In my mind I had the idea maybe the engine gets gas from the main jet which maybe should not happen as long rod and jet is in good shape and correct adjustment. His problem got solved very uncommon and sad: He is 75 as his car and lost the driver license because of dementia, so his car is not on the road anymore.
I know, working on a carb is hard stuff with multiple problems, but I work in a systematic way and hope to have success soon. Systematic way means:
First: Find out all problems and how they are connected maybe. Learn how it should work.
Second: Fix everything step by step.
Try here, try there, without plan and logic follow up will not create success. Doing it step by step will end in a success.


Stefan Germany (now in hurry to work)

"I know, working on a carb is hard stuff with multiple problems, but I work in a systematic way and hope to have success soon. Systematic way means:"

Stefan,guten Tag

The W-1 carburetors are extraordinarily simple. Chevy owners manuals of the day and shop manuals explain how they work.

People who work on these carburetors for money would like for you to think they are complex but that is simply not true. Examples of complex carburetors are the Rochester Quadrajet and the Carter Thermoquad.

If you find an explanation of how they work that will be a good starting point.

Original Carter carburetor repair kits include detailed rebuilding instructions. If you decide you want one of my original Carter needle/seat assemblies I will copy the Carter repair instructions and include them with the needle/seat.

If you have the correct internal parts in that carburetor and if it is the original carburetor for your year car it should work "OK" once the needle/seat are replaced and the float level is set. For perfect running some experimentation with different main jets and metering rods will achieve your goal.

It seems that you are making this more complicated than it is. If you read a description of how these carburetors work you will see how few parts are actually in them and how simple they are.

There are a few tricks to getting them apart without damaging the soft brass plugs, jets and check valves but complexity is simply not part of the challenge. You can do it!

Aufweidersehn,

Ray Waldbaum

Hi Ray,

I made an overhaul using an overhaul kit by filling station last year, so I have the drawings how to overhaul the carburetoir. But I know, the carburetor in my car came from a much younger car than mine is. I found some parts at ebay.com, but what I am still searching for, is the metering rod jet stamped or marked with 95 for the 1940 standard metering rod marked 67-40. 67-40 needles I did find and buy at ebay.com and am waiting for them.

Actually in my car is a 93 jet passage and a 67-46 needle, for sure both wrong for the 1940 car.

And I am still searching for an answer how it is possible at my old pals car to close the idle mixture needle down to zero, completely closed, and the engine does still run. From where does the gas come from to keep the engine running? In my mind there are not much possible reasons:
1.) The float chamber level is much to high and the gas finds a way offside the normal passages.
2.) The metering rod adjustment is not correct.
4.) The idle needle is damaged.
5.) Other suggestions?
4 I may exclude, that needle is brand new.
The other I will check when I visit my pal next time. Not easy, he lives about 600 mls away.
He was at a carburetor specialist and even the specialist could not find out what is going on with that carburetor.

but on first place I want to get mine back to original condition including the right metering rod and jet passage.

Do you speak german?

Best regards
Stefan

Stefan,

I was a lousy student in both high school and college with one exception. For me learning languages was as simple as breathing. I entered college in the fall of 1962, USC (University of Southern California). Freshmen were given placement exams in foreign language, and other academic subjects. I got a summons from the language department chairman telling me that I had just recorded the highest score ever recorded in the German language placement exam and offered me a scholarship if I would be a German major.

Having the wrong temperament to wear a suit and work as a translator at the United Nations I thanked him for his offer and declined. So, being a basically poor student I found myself interested in geology and majored in that, getting mostly grades of C and occasionally lower.

My performance on the German exam resulted me being placed directly into graduate level courses as a 17 year old freshman and getting straight A grades. If not for that I would have been placed on academic probation and kicked out.

That was 50 years ago and I've forgotten all that German.

With regard to your carburetor, if the idle mixture screw has no effect there is a massive internal leak. Sometimes so much air is leaking in along a worn throttle shaft that even closing the butterfly does not kill the engine.

When I have put bushings in the throttle shaft bores in carburetors it eliminated that air leak and vastly improved idle quality and the way the carburetor responds to the mixture screws.

If your "expert" can't figure out the problem he's not much of an "expert".

Hello germanchevy:

I have brand new original Carter metering rod jets for almost all of the Carter W-1 carbs. I have a New Old Stock - NOS #95 metering Rod Jet. You can have it for $1.50 + shipping.

dtm

hello dtm,

fantastic! If I trust my old parts book the #95 jet is the right one for the 1940 car with Standard metering rod and I thank you for your offer to sell one to me.
would you please calculate the total amount and lets find a way to pay it.
At ebay I found standard metering rods without jet and "lean" rods with jets so a standard jet is the last missing part.

Best regards
Stefan

Regards
Stefan

Send me you entire address in a private message ( PM ). I will then go to the US post office and ask for the price to ship it to you.

dtm