The Stovebolt Site Forums The Shop Area Engine Shop what is a rochester "c" carb???

my 46 ton and a half has a rochester "c" carb. i have not been able to find anything at all about it. i got a rebuild kit locally for a "b" and most of the parts look as if they will fit. am i using the wrong kit? any info would be helpful.

First, as Rochester made their first carburetor in 1949, you can easily see that no Rochester would be original for a 1946 truck.

I am unaware of any Rochester type "C" carburetor. However, Rochester would append a "C" to the end of the carburetor type to denote integral automatic choke. The type "B" carburetor has a manual choke. If it were used with an integral automatic choke, it becomes a type "BC". If used with a divorced (sets on the manifold) choke, it becomes a "BV" (the "V" chosen because of the vacuum choke pull-off required with the divorced type choke).

This same convention also used with the 2G (2 barrel) and 4G (4 barrel) Rochester carburetors.

Jon.

Rochester also had a monojet carb which can bolt in place of the B series, and also the Corvair carburators, which don't have power enrichment circuits.

The Corvair carb were known as a model "H" with the "HV" having the vacuum pull-off. The monojet is the model "M" and "MV". Rochester also had a model "R" and "RC" (sidedraft 1 barrel), but these are seldom mentioned as most hobbyists have never heard of them (and I wish I hadn't!!!).

Jon.

on the bottom front of the carb it is marked "rochester GM C" very clearly. the choke is of the manual type. it seems to be a "B" except for that front marking. any clues?

My Doug Roe book on Rochesters mentions a model before the "B", I'll have to look at it tonight and see what it is called, that may be what you have.

The model prior to the B is the AA used on 1949 and 1950 Oldsmobile. 2 barrel downdraft with horizontal air intake (and a gear driven accelerator pump!).

Jon.

regardless of b or c or whatever, how many parts from this "B" rebuild kit can i actually use? are there supposed to be so many extras?

homer - the answer to how many parts you can use depends on the kit.

50 years ago carburetor rebuilding kits produced by the major companies contained parts which would only rebuild one or two carburetors; typically a kit would contain gaskets, fuel valve, accelerator pump, main jet, idle jet, idle mixture screw, return springs, check valves, linkage rods, and clips. There would be no extra parts in the kit. Due to the fact that a kit would only service one or two different carburetors meant that the auto parts stores had to stock an immense inventory of different kits. This condition created a "need"??? for a more universal (and less expensive) kit.

Most of the major companies (as well as all of the cut-rate companies) then started producing a "clean-out" kit which consisted only of gaskets, fuel valve, pump, and clips. This still produced too many different kits for the auto parts stores to inventory.

Then some "wise"??? individual determined that the major cost of each kit was the fuel valve and the accelerator pump. Enter now the "univeral" kit. A database was then prepared (today we would call it a spread-sheet) that listed each combination of fuel valve and accelerator pump; and all of the carburetors these two items would fit. Now all of the various gaskets used in these carburetor would be added to the kit and charge the customer a little more for the unused parts. This resulted in a tremendous decrease in the number of kits, reducing the inventory of the parts houses, and increasing their profit. The customer was then told to compare the original gaskets with those in the kit, and use the proper gaskets (I have never been told how the novice customer is to recognize if an incorrect gasket had been installed previously).

Assuming you have one of these kits with a bunch of extra gaskets, you basically have to determine which of the major gaskets (airhorn and throttle body) is correct for your carburetor. The rest go into either the trash or your "maybe I'll need it sometime" bin of unknown parts. The accelerator pump and fuel valve should be used as well.

Jon.

jon, thanks. it apears that the gaskets and springs are a match but the pump is a no go. this carb seems to be a mystery rochester "C" (in to a "C" on the label , all the numbers end in c) and i have a kit for a "B". should i bother to find the right kit? thanks again

homer - the type "B" was produced from 1949 to 1967. SEVERAL different pumps were used during this time. We make probably 50 different repair kits for the various model B Rochester carburetors.

Jon.

Homer has asked a question we've always wanted to ask. The carburator on our stock '51 3100 has a box on the front of the airhorn with Rochester diagonally in the middle, C in the upper left corner, and GM in the lower right corner. The box is just above the fuel inlet. It has a manual choke. We rebuilt it successfully with a Rochester B rebuild kit, but always wondered what the 'C' stood for.

Interesting. My truck has a Rochester on it too. Was this considered an upgrade from the stock carb for 46's?

OK - A little SPECULATION here.

First, let me state there is NO MENTION in any of the published Rochester documentation from the beginning in 1949 up through current offerings about a model C (other than the C meaning integral choke as mentioned earlier in this thread).

HOWEVER - In 1923, Carter Carburetor received its first MAJOR retail order from Chevrolet. At this time Carter did not have sufficient plant space to fill the order from Chevrolet, and Chevrolet was given license to produce Carter Carburetors in the Flint plant. Carter Carburetors produced by Chevrolet were identical to their Carter produced cousins EXCEPT numbered parts were numbered with the Chevrolet number rather than the Carter, and the castings carried a letter "C".

As GM owned Rochester, the Rochester B (unfortunately) became the standard 6 cylinder carburetor for Chevrolet in 1950, replacing the much superior Carter W-1. Possibly some other historian with actual data will jump in here; but I am SPECULATING that possibly history repeated itself, and these carburetors with the C were actually produced by Chevrolet. Repeat - SPECULATION ONLY AT THIS TIME.

Jon.

As an addendum to the above post: The URL http://www.thecarburetorshop.com/CarterW1comparison.jpg is a picture of two Carter model W-1 part number 574S (1946 - 1948 Chevrolet). The one on the left was built by Carter in St. Louis, the one on the right was built by Chevrolet in Flint. Look close, and you can see the large letter "C" in the center of the end of the bowl on the carburetor on the right. I apologize for the quality of the picture. I have not yet mastered the digital camera with contrast in black.

Jon.

Good info, CK!
Maybe I can shed a little light on the subject, as my family's shop was very active in the carb rebuilding business in the 40's, 50's, and early 60's. Carter was NOT pleased when Rochester started equipping GM vehicles with original-equipment carbs in the early 50's and the owner of the company vowed to sell a million replacement carbs for Chevy vehicles! That's why so many retro-fitted vehicles are found with Carter carbs now. Even as late as the Quadrajet days, some QJ carbs were manufactured by Carter to satisfy a "restraint of trade" lawsuit against GM by Carter! Somewhere in the massive repair manual library left over from the family shop, I believe there are some original Rochester, and Carter repair manuals, so I'll try to do a little research on this thread.
Jerry

Jerry - Carter produced millions of Q-Jets under license from GM from 1966 to the late 1970's. The Q-Jet was (and is) one of the finest street carburetors ever built at any price. There were some "teething" problems in the early years, but by 1968, this was a fine carburetor.

As to the replacement carbs for the Chevy 6, if I drove a 6 cylinder Chevy, it would have a Carter. Both the Carter W-1 which was replaced by the Rochester B and the newer Carter YF are superior to the Rochester B. Of course, if the car is a "showcar", one is stuck with the original carb.

Jon.

Carbking, I have a 261 with the correct Rochester B on it(bigger throat and main jet than the carb for the 235). The throttle response is very "notchy" and I wouldn't mind replacing it with a superior Carter model. Do you know if there was one made which was big enough to retain all the power capability of the 261(I don't want to restrict the engine by putting too small a carb on it although I know it will run on one).

I'm interested too, my B has been requiring a needle/seat replacement annually.

Carter made replacement YF carbs for Chevrolet the smaller Chevy 6's (up to 235). Would suggest not using these on the 261.

Foorrdd used the YF on the 300 CID 6. Would suggest hitting the boneyards, and acquiring one of these from a late 60's or early 70's (the earlier, the better, as less smog calibration) Foorrdd truck for use on the 261. Should be readily available and cheap. Foorrdd sold lots of 300's. I take no responsibility for your speeding tickets. :p

Josiah, not much I like about the B, but it isn't fair to blame fuel valve (needle and seat) failure on the carb. A few years ago, the major manufacturer of repair kits started eliminated the "staking" on the fuel seat to save a few pennies. Next time you change the fuel valve, try the following:

Assemble a chuck of 2x4 lumber about 4 inches long, a drift punch slightly smaller than the ID of the fuel valve seat (the plunger portion, not the orifice), a ball peen hammer, and the used steel check ball that you are replacing in the carburetor. Place the thread of the seat on the 2x4, place the ball inside the plunger area on the orifice seat, place the drift punch on top of the ball, and whack (highly technical carburetor term - whack ) the punch with a hammer. Hit it one time only. This will form a tapered seat for the needle, providing better sealing and longevity.

Good idea. I wasn't really blaming in on the carb, but the Keihin carbs in my motorcycle are still on their original 1974 needles and seats with 45,000 miles on them.

Nothing annoys me more than having about a cup of gasoline pour on the hot exhaust manifold.

I have the same thing. Model "c" I'll take a pic and post it up tomorrow. Hope my "b" rebuild kit works.

I’m hesitant to resurrect and old thread like this but I was wondering if there is any new insight on the Rochester C carb ? By reading this thread, I found out that my carb is not stock to my 1941 Chevy pickup. My carb is also the Rochester C and I guess that I will use a “B” kit for the rebuild.

Rochester Carburetor Bulletins/Manuals

AA, B, BB, & BC one-"barrel" are shown.
The 4GC 2-barrel is also shown ("basically two dual carburetors").

Hey Okie,

I have one of these mystery Rochester B carbs marked with a 'C'. I rebuilt it using a cheap Rochester B rebuild kit and it worked fine.

You might check to see if (and how much) the air horn and float bowl are warped while you have it apart. You can see my postings on this of a month or two ago. Good luck with it. As you probably know by now there was no Rochester C carb...only the ones shown in the link Tim provided.

Thanks Jon for the tip.

Here are some pics of the markings on my carb.

https://photos.google.com/share/AF1...M1d4YnJhR2pyT19NRkJtYXhSNWlyTjVwSFJiUE9B

That looks like a regular model B. There were variations but basically all were similar. The B kit should be ok. Watch the manifold gasket. The one in the kit might cover a vacuum passage. Clean it well, check for warpage and see if you can tell which jet size it has (out of curiosity mainly...to get an idea of what has been done to it). It is important to get the power system working as well as possible.

Plz help I.D. Please see photo. It's stamped "c"
On top of a 1952 216

It is a Rochester B. Please ignore the "C." If you read the first 3 pages of comments on this thread, you'll see the letter C stands for something but it is not really all that clear and the egg may not be unscrambled at this point. If you search using Rochester B, BC as your search keys you will find a lot of information on these over the past 2 or 3 months. Good luck.

Thanks Jon, happy Friday!

I am having the same problem. I have a 1959 Chevy Apache with the 235 inline 6. Stamped on the front of the carb is a square in the top left of the square is a C from the bottom left to the top right corner it says Rochester and in the bottom right corner is stamped GM. I have no idea what rebuild kit to order. I also have a manual choke. I am losing power as I accelerate so clearly the accelerator pump isn’t working. Does the kit you have replace the accelerator pump?