How To ID A WWII 539S Carter Carb

[Chuck Lutz]

Pending something definitive on the introduction of the 698S at Carter, the best I can estimate is a 1948 introduction and when it was adopted along with the 539S for the Model MB 4x4 is even later. So how do you know if you have a "correct" 539S for your jeep...not a firetruck, pump, genny, or any other special use vehicle? Well, there are four major components which contain many parts that are also interchangable so let's look at the beginning.

Choke Tube (Air Horn):
See the "C" in a circle near the top? That is NOT found on a 539S.

Carter 636S Front.jpg (182.51 KiB) Viewed 24744 times

Bowl Cover:
See below the CARTER WO where there is a "C" in a circle? This is a 539S cover. If it has "146 94" or "146 249" those are later production.

539S Cover DE.jpg (51.91 KiB) Viewed 24736 times

The Bowl has EIGHT patents, last is dated 1936. If it has TWELVE patents, it is later production.

539S Patents EIGHT.jpg (144.84 KiB) Viewed 24734 times

OK, only THREE pics per post, let's move on...

[Chuck Lutz]

OK...

Throttle Body (flange):
It has "407" stamped into the gasket surface (a 698S also does), but "505" is for a 636S Carter and "458" is for a Carter 596S.

Carter 539S 407 Number DE.jpg (67.76 KiB) Viewed 24710 times

The linkage on the Throttle Shaft is a dead giveaway also, with the Carter 539S and 698s using this three-armed style:

Carter 539S Base NOS.jpg (54.16 KiB) Viewed 24701 times

The 596S and 636S use a different linkage setup:

Carter 636S Linkage Patent.jpg (43.11 KiB) Viewed 24703 times

Much of this comes from Claude Pons' excellent guide and the pics from Derek and others who posted them....thanks!

[Johnr]

Nice post Chuck,

Some more info here:

http://www.42gpw.com/carbs.htm" onclick="window.open(this.href);return false;

Cheers

[Derek Eddlestone]

Good work Chuck. Hope it begins to unravel the mysteries of the Carter WO.
and may lure people away from the later Solex carb that seem to be popularly fitted.

John,

A quick look at the picture from the link you posted and you can see the Circled C on the Air Horn where there shouldn't be one and 12 Patent numbers where there should be 8 on a carb that is identified as a WO 539. The gold colouring also suggests a post war item.

This is a picture of the WO 636(right) and 539(left). Externally the carb bodies look identical. Some minor linkage differences will be pointed out. Thanks to Mr. R. Adams for the pic.

Derek.

[Derek Eddlestone]

John,

I believe this picture may be a more accurate shot for the link you posted.



.........and from another angle :-



Derek.

[Chuck Lutz]

I think one of the weaknesses of the design for 539/596/636/698 type carbs is the WEARING of the Throttle Shaft and the Throttle Body steel itself which lets air leak into the carb. I have heard countless stories here and at the jeep meets about guys who bought the GOOD rebuild kit (Ron has them) and even with some tools and a set of the rebuild instructions....could not get their carb to work properly. I would immediately suggest they try any of the tests to see if air is being sucked in around the throttle shaft (carb cleaner or other things squirted at the shaft ends when running) to determine if that is a potential problem before checking for blocked passages, set-up problems or other issues related to proper carb/jeep tune ups.

I have had the opportunity to wiggle a few of the shafts in these carbs in an attempt to teach myself how much wiggle MIGHT be found and how much CAN be found in working carbs....but so far it seems that if you can get dang near ANY movement of the throttle shaft....then you are probably sucking in SOME air and maybe this is why the carb has suddenly become "available" for you to purchase!

So if you have a 539S in your old parts locker that you took off because it would just not run "correct" even after a rebuild....and you slapped on a SOLEX as the solution to that....let me know what you want for that 539S....and how many of the four major components are still on it.

I'm interested in buying them!

OK, I'll come clean here: The Throttle body CAN be bushed by a COMPETENT machinist, but must be drilled out PERFECTLY so the bushings and the new hole in them will fit the throttle shaft PERFECTLY or else the throttle shaft will BIND or....leak air even worse than before!

Given the prices that a 636S or a 698S are going for when advertised as "correct" for a WWII MB/GPW.....and they are NOT a "correct" WWII MB/GPW carb!.....I think a truely CORRECT 539S with all the proper parts on it is worth spending the money to have bushed if it needs it by a pro if you are not one, and THIS will be the kind of insurance you would want if building a CORRECT WWII MB/GPW CARB is your goal.

Now....would some kind soul (Derek?) please post the measurements of the throttle shaft hole in an NOS Throttle Body and the measurements of an NOS Throttle Shaft so we can add that to the checklist for a rebuild? I believe the dimensions are different for a 539/698 which use the "407" marked throttle body vs. the 596/636 which use the "458" and "505" marked ones....so if you have the dimensions for those as well, that would be cool also. From those measurements we can determine what the FACTORY difference between hole and shaft is and that would help us to determine just how much "wiggle" they are SUPPOSED to have (hardly any I imagine!).

Thanks!

[Johnr]

John,

I believe this picture may be a more accurate shot for the link you posted.

Thanks Derek! You are quite right and that's a much better pic.

That top pic should get most people sorted as to which carb they have.

Cheers
John

[Yonder]

Chuck, I have ofted wondered, should the throttle shaft be regularly lubricated at each end, and also the choke shaft ? Or would the gas/air mixture wash the lube away straight off? Maybe there's a special thick oil that would do the trick and reduce the wear on the throttle shaft and the steel housing, and at the same time stop the air entering the carb at that point. Just a thought...

[Chuck Lutz]

I think regular usage will keep the choke shaft and throttle shaft from seizing up and no lubrication is required. Remember that it took the last 50-60 years to wear out that throttle body/throttle shaft so I would not worry about that too much. Bushing or rebushing are always an option when they DO wear out and begin sucking in air and messing with your purrr-fectly running engine. As the supply of parts is used up, I forsee at some point that the Throttle Shaft (brass) will need to be turned down so it is ROUND again and bushings inserted in the Throttle Body to compensate for that egg-shaped wear and leaking air problem. That's one way to solve that problem in the future!

Now, let's look further. Is the EIGHT patent bowl a guarantee that your carb is a 539S? Well, no it is not. Carter used that bowl with a few slight changes for several carburetors, so simply using that as a guage to determine the pedigree of a carb is not accurate. Remember that the 596S which appeared on the Aug. 1945 Carter Bulletin as used on the Agri-Jeep (and later on the very early CJ2A) has an EIGHT patent bowl, but you have to know the slight changes to tell which bowl it is and get a sense as to what carb it is from because it is not the SAME eight patent bowl that the 539S used!

Next, we have to understand where the 698S fits into the picture. While it has TWELVE patents, it does use the 539S Throttle Body with the "407" stamping and throttle shaft/linkage. How did it appear AFTER the 596/636 were in use and WHY does it have the same throttle body when the 596/636 carbs use a different one? Quite frankly my dear, I haven't the foggiest idea, wot!

Well, maybe some changes/improvements came along that ARE different internally from the 539S so it did need a new designation (the low speed jet size comes to mind) so it superseeded the 539S so to speak, and certainly the additional fittings on the throttle linkage that the 596/636 use were not needed on a standard MB/GPW that had a 539S on it so the 698S did not need them either.

What I have not determined is how the "Carburetor Salads" came about....did Carter use up existing parts on some newer carbs? Well, I would think they would use them as "spares", but if the "old" part...let's say a bowl cover....met the specs of the new part, then perhaps it was a "use until exhausted" item. Personally I do not put much faith in this theory.

Did the motorpools or rebuild programs such as those at Esslingen, Japan, the various US rebuild facilities and programs and other "in service" shops mix up parts? Well, by the time of the Korean War, the MB/GPW was still in service but the 596/636 Carters were in use by then and no matter where they obtained the parts, if "parts is parts", then I suppose when they tore down 100 carbs that no one put the same parts together and if you look at Nabholtz pg. 63...he mentions not only the 1943 rebuild program, but the 1951 rebuild program that used 596s and 636s so those and their associated components were in the gov't parts inventory. No wonder you find a lot of carb salads and why complete 636 carbs are found on WWII jeeps.

I also think that over the years, the big rebuilding facilities in the civilian market knew which components DID and DID NOT work on one another and had no problem whatsoever in mixing them up to produce the best rebuilt carbs they could. Originality of parts was secondary to how well they worked!

So when you find a Carter WO you think might be a good replacement for the SOLEX the PO put on your jeep, before you sink some time and money into it, perhaps you want to find out if it has one, two, three or four of the major components from a 539S on it if ORIGINALITY is important to you.

(Thanks again to those who have posted pics here and to those on Ebay I have used....they are what makes this much easier to explain!....you know who you are....Derek!)

[Greencom]

I've seen a WO with 9 patent dates on it. Great information by the way, thank you.

[Chuck Lutz]

All right, for those who have found all the major components and are ready to rebuild your carb, what other things are important?

Well, if you don't have at least a couple of the correct tools, it is harder to rebuild them, so that's an issue that is explained in the kits and in the TMs and elsewhere so I won't address that.

How to clean it up? Sone guys sandblast them, then plate them (and do this to the linkage also) and some guys use sodablast because it can be rinsed out with water and not get stuck internally. High pressure air will remove the remaining moisture. I think this sounds good to me and Derek has posted pics (I have used them) of shiney carbs that have been done this way and has mentioned that this will oxidize and the finish return to an almost original state....so I think I favor this over a sandblasting!

Some guys use a type of Parkerization on the Throttle Body, but Derek also found a can of BLACK PAINT from Carter that was to repaint them so I think a slightly semi-gloss finish would be an option closer to factory specs. Interestingly enough, the two carbs just sold on Ebay with their post-war cardboard boxes in the photos appear to be 698S....but do NOT have even a semi-gloss appearance....they look unfinished. Remember they are not contained in Carter boxes, and may not have been direct from the Carter factory....it is not possible to tell without a closer look and even then it may not be able to be determined if they are 100% as-produced.

(Note: since I posted this I have come to believe that a phosphate finish on the flange body is correct and the Carter (or other) paint is only a later-introduced product for rebuilding only and never used on original 539S or even the 698S carbs!)

One more thing to keep an eye out for....the "Throttle Connector Rod" on an original 539S is part number 115-59 and has a unique attachment to the Throttle Arm on the Throttle Shaft....a SPRING and a round KEEPER hole the Arm to the ROD.....the later carbs including the 596S, the 636S and the 698S use a different Rod with a part number 115-142. It uses the clip to hold the Arm to the Rod. For the discriminating 539S rebuilder, the piece de resistance is having the correct Rod and the Spring and Keeper!

Here is the 539S Throttle Rod, Throttle Arm, Spring and Keeper:

Carter 539S Choke Arm Keeper.jpg (42.26 KiB) Viewed 24232 times

The later style arm and clip are easy to identify, see the clip on the arm/rod:

Carter 636SA Base.jpg (71.39 KiB) Viewed 24237 times

Here are the two Rods:

Carter 636 and 539 698 Throttle Rod.jpg (70.79 KiB) Viewed 24232 times

Now for the BAD news....there are currently NONE of the overhaul kits available that I am aware of that use the 539S style 115-59 Throttle Rod.....they all use the later style 115-142 from the 596/636/698 style carbs....so do not replace those parts! Try to keep them if a CORRECT 539S is your goal!

If not...send the Rod, Spring and Keeper to me.....I need a few of them for future rebuilds!

[Derek Eddlestone]

Now....would some kind soul (Derek?) please post the measurements of the throttle shaft hole in an NOS Throttle Body and the measurements of an NOS Throttle Shaft so we can add that to the checklist for a rebuild?

Chuck,

I have NOS 539S shafts here and they are 0.3125" or 5/16". I don't have any NOS bases here to measure but there must be a standard clearance which I would imagine a machine shop could tell you.
I like the detail you are going in to in your posts and here's another little thing to look for in a 100 point restoration. These Insulators (183-19) are correct for both 539S & 698S and also appear in late '40s Carter books.







Derek.

[Chuck Lutz]

Thanks Derek....and I would like to point out that your Feb 1942/Nov 1944 Carter Service Bulletin incudes ONLY the 539S and does not yet mention the 698S! I would like to see a 1945 or 1946 or 1947 Revison of the Feb. 1942 Military MB 4x4 539S Carter bulletin to see when it DOES show up as a replacement! I'm still thinking 1948ish.

Mark Tombleson's Willys BOM for 2/5/45 only lists the 539S.....

[David H. Morganthall]

Have you guys looked at the carbie cheat sheet lately? The 698S seems to arrive on the scene in June 1943. I have one or two that still have the tags on them and appear to be unmolested. They match closely to the cheat sheet and also happen to coincide with my son's July 29, 1943 GPW carbie.

[Chuck Lutz]

That is part of the problem David.....

The 698S does not appear in ANY WWII documents we have seen so far. If anyone has something from Carter, Ford, Willys or the gov't...that states anything to the contrary, would they please post it?

The introduction of the 698S at Carter is unknown.....it may have been produced anytime, however if you go through the Carter Service Bulletins or all the Carter applications, you will find that the NUMBER seems to be chronologically issued....the higher the number, the later it was introduced. If you look at ENOUGH of them this seems to be the case....I put a list of those I found on a thread called "CARTER 539S 698S 636S DATES".

Look at Derek's Carter Service Bulletin with the Feb. 1942 Revison Nov. 1944......and it only shows the 539S......but if you look at the Feb. 1942 Revision June 1952....it lists the 539S AND the 698S.....

I believe the 698S arrived on scene in about 1948....and when it made it into the government systems happened between that date and the June 1954 date that bulletin mentions.