Rochester Model B Carburetors

Model B History and Identification

1958 Chevrolet Truck Rochester Model B Carburetor – Restored by The Carburetor Doctor

Starting in 1949, the Rochester Products Division of General Motors produced carburetors for GM products and other makes as well. The first Rochester carburetor was the AA two barrel used on the new Oldsmobile Rocket V-8 of 1949, followed by the model B one barrel in 1950 on Chevrolets. Model B’s were used from 1950 to 1967 on GM 4 and 6 cylinder applications. They were also sold as replacement carburetors for 1932 and up Chevrolets originally equipped with Carter W-1 or Stromberg BX series carburetors.

Model B carbs are named according to the type of choke they used:

  • B: manual choke carburetor
  • BC: automatic choke, choke coil mounted on the side of the carburetor (1950-1962)
  • BV: automatic choke, choke coil on the intake manifold (1963-1967)
1st Design Pump – Slotted Stem, Leather Cup
2nd Design Pump – Round Stem, Rubber Cup

Model B Designs

Internally, there are two main designs: the 1st design with a non-rebuildable leather pump that has a flat stem, used on cars up to 1956 and on trucks up to 1962, and the 2nd design with a rebuildable pump with a rubber cup and a round stem, used on cars from 1957 and on trucks after 1962. To complicate things there have been leather pump kits sold for 2nd design carbs, but still with the round stem. Also, the 2nd design, round stem pumps, come in two different lengths, 2 3/4″ and 2 13/16″. We have both 2nd design pumps available in our kits. Cheaper kits provide just the pump cup. We don’t sell these in our store since the pumps themselves are often worn or damaged – changing the cup won’t help in those cases. Neither will it help if you have one of the non-rebuildable leather replacement cups that were sold at one time.

After two years of production the 1st design carburetors were revised to deal with leaks from the top gasket between the float bowl and airhorn. Starting in 1952, the airhorn casting is heavier and is retained with larger 12-28 Fillister head screws until the end of production in 1967. Today these screws are nearly obsolete, so replacing chewed up old screws has been problematic. To fix this, we’ve introduced a line of master kits with the correct screws and other hard-to-find parts to service all Model B carbs.

Rochester Model B Design Features Summary

1st Design

2nd Design

early late long pump (2 13/16″) short pump (2 3/4″)
years 1950-51 1952-1962 1957-up 1963-1968
pump type slotted stem, leather slotted stem, leather round stem, rubber round stem, rubber
airhorn screws 10-32 12-28 12-28 12-28
choke type manual (B), integral choke (BC) manual (B), integral choke (BC) manual (B), integral choke (BC) manual (B), remote choke (BV)
standard kit CK10 CK10 CK33 CK31
master kit MK10A MK10B MK33 MK31
1st Design Model B Manual Choke Carburetor, 1950-51 Models (10-32 Airhorn Screws), Clamp-On Oil Bath Air Cleaner
2nd Design Automatic Choke Carburetor Model BC With Wing Nut Air Cleaner Attachment (1957-up)
2nd Design Automatic Choke Carburetor, Model BV, 1963-up

 

Master Kits

Our master kits for Rochester Model B carburetors include the following items:

  • correct airhorn screws and lockwashers
  • complete accelerator pump assembly (ethanol compatible)
  • pump duration spring
  • pump return spring
  • idle mixture screw and spring
  • brass float
  • needle/seat (ethanol compatible)
  • gaskets, clips, seals, check balls
  • mounting gasket
  • instructions with exploded diagram
MK10A: 1st Design, 1950-51, 10-32 screws, leather slotted pump
MK10B: 1st Design, 1952-1962, 12-28 Screws, Leather Slotted Pump
MK31, 2nd Design, 1963-1968, 12-28 Screws, 2 13/16″ Round Stem Pump w/ Viton Cup
MK33: 2nd Design, 1957-1962, 12-28 Screws, 2 3/4″ Round Stem Pump w/ Viton Cup

 

Standard Kits

Standard kits are an economical way to rebuild a carburetor in good condition. They don’t include floats, springs or screws but all of ours feature:

  • complete accelerator pump assembly (ethanol compatible)
  • brass float
  • needle/seat (ethanol compatible)
  • gaskets, clips, seals, check balls
  • mounting gasket
  • instructions with exploded diagram
CK10 Rebuild Kit for All 1st Design Rochester Model B Carbs
CK31 Rebuild Kit for 1963-1968 Rochester Model B Carbs With 2 13/16″ Long Pump
CK33 Rebuild Kit for Rochester B Carbs With 2 3/4″ Accelerator Pumps

 

Stromberg WW Carburetors for GMC Trucks

Until 1966 GMC light trucks used mostly GMC engines; after that they shared drive trains with Chevrolet. Medium and heavy duty GMC trucks used their own gasoline engines until 1974.

In the 1960s and 70s these were mostly V6 engines ranging in size from 305 CID to 478 CID; there was also a 503 CID straight 6, a 637 CID V8 and a 702 CID V12. All of the V6 and V12 engines used Stromberg WW or WWC carburetors; the V12 used two of them. We have complete listings of GMC carburetor kits and parts here.

The Stromberg WW-series came in two main variations, the WW and WWC. The WW is the smaller of the two, and is often mistaken for a Carter BBD carburetor. In fact, Stromberg WWs and Carter BBDs were used interchangeably on Mopar applications.

Stromberg WWC for GMC
Top view of a Stromberg WWC carburetor.
Stromberg WW for GMC
Front view of the smaller Stromberg WW carburetor

One quick way to tell a WW carburetor is that it has a large accelerator pump lever across the top of the carb. WWC carbs don’t have this lever.

There are many versions of these carbs that look similar, so it’s essential to check the carb number when ordering a kit. The carb number appears on these in a couple of different places. As shown in the pictures, it’s often on a round tag that looks like a washer on the top of the carb. This will usually have the vendor number shown in the table below. Sometimes there is a conventional tag with a GMC number. In many cases there is a ‘Code number’ stamped onto the top part of the carburetor – on the flat area on the float bowl cover.

All WW carburetors use our F77 float, listed here. Unfortunately, there aren’t any new floats for the larger WWC carburetor.

 

 

Stromberg WW/WWC Carburetors for 1960-66 GMC Applications

Year Engine Type GM Part No. Vendor No. Code No. Notes Carb Kit Float
1960 305C V6 WW-2 2391843
2391844
380977
380980
23-123A
23-124A
CK4491 F77
1960 351 V6 WW-2 2382770
2382773
2382774
380972
380973
380974
23-120A
23-121A
23-122A
CK4491 F77
1960 401 V6 WWC-3 2382772 380978 23-125 CK738
1960 702 V12 WW-2 2382773 380979 23-126B uses 2
7000
CK49 F77
1962 305C V6
305D V6
WW 2427805 381031 23-133A except
L-4000
CK4491 F77
1962 305C V6 WW 2427807 381033 23-135A L-4000 CK4491 F77
1962 351 V6 WW 2433601 381038 23-137 except
L-5000
SP-5000
CK4491 F77
1962 351 V6 WW 2433602 381039 23-138 L-5000 CK4491 F77
1962 351 V6 WW 2433603 381040 23-139 SP-5000 CK4491 F77
1962 401 V6 WW 2433608 381045 23-144 F77
1963 305E V6 WW 2445281 381076 23-151 1000 to
3500
CK4491 F77
1963 305C V6 WW 2445281 381076 23-151 4000 except
L & LH-4000
CK4491 F77
1963 305C V6 WW 2445282 381077 23-152 L & LH-4000 CK4491 F77
1963 351 V6 WW 2433601 381038 23-137 5000 except
L & LH-5000
CK4491 F77
1963 351 V6 WW 2433602 381039 23-138 L & LH-5000 CK4491 F77
1963 351 V6 WW 2433603 381040 23-139 SP-5000 CK4491 F77
1963 351 V6 WW 2433606 381043 23-142 Hydraulic
Governor
CK4491 F77
1963 401 V6 WW 2440817 381064 23-147 CK738 F77
1963 478 V6 WW 2440818 381065 23-148 CK738 F77
1963 702 V12 WW 2433607 381044 23-143 uses 2
7000
CK49 F77
1964
1965
305E V6 WW 2453827 381094 23-153A except
L-Series
CK529 F77
1964
1965
305C V6 WW 2453827 381094 23-153A except
L-Series
CK529 F77
1964
1965
305C V6 WW 2456769 381103 23-158 L3500
L4000
CK529 F77
1964
1965
351 V6 WW 2433601 381038 23-137A except
L & SP series
CK4491 F77
1964
1965
351 V6 WW 2433602 381039 23-138A L4000
L5000
CK4491 F77
1964
1965
351 V6 WW 2433603 381040 23-139 SP5000 CK4491 F77
1964
1965
351 V6 WW 2433606 381043 23-142 Hydraulic
Governor
CK4491 F77
1964 401 V6 WWC 2440817 381064 23-147 except W5000
SP5000
CK738
1964 401 V6 WWC 2433601 381038 23-137A W5000 CK4491
1964 401 V6 WWC 2441975 381066 23-149 SP5000 CK738
1964 478 V6 WWC 2441975 381066 23-149 SP5000 CK738
1964 478 V6 WWC 2440818 381065 23-148 6500 CK738
1964 702 V12 WW 2433607 381044 23-143 uses 2
7000
CK49 F77
1965 305E V6
305C V6
WW 2472952 381123 23-160 except
L Series
CK50 F77
1965 305E V6
305C V6
WW 2472953 381124 23-161 L3500
L4000
CK50 F77
1965 351 V6 WW 2472954 381126 23-163 except
L & SP series
CK526 F77
1965 351 V6 WW 2472955 381127 23-164 L5000 CK526 F77
1965 351 V6 WW 2472956 381128 23-165 SP5000 CK526 F77
1965 351 V6 WW 2472958 381131 23-168 Hydraulic
Governor
CK526 F77
1965 401 V6 WWC 2472960 381134 23-171 All H Series CK738
1965 401 V6
478 V6
WWC 2472961 381135 23-172 SP5000 CK738
1966 305C V6 WW 2485214 381164 23-181 HM-5500 CK50 F77
1966 351C V6 WW 2485215 381165 23-182 HM-5500
HM/JM-7500
CK526 F77
1966 351C V6 WW 2472955 381127 23-164 TM-7500 CK526 F77
1966 351M V6 WW 2487147 381168 23-185 RM-7500 CK738 F77
1966 351M V6 WW 2483900 381167 23-184 HM/JM/TM-7500
HM/TM-8500
CK738 F77
1966 401M V6 WW 2483900 381167 23-184 HM/JM/TM-7500
HM/TM/JM/WM-8500
CK738 F77
1966 401M V6 WW 2487147 381168 23-188 RM-7500 CK738 F77
1966 478M V6 WW 2487147 381168 23-185 RM-7500 CK738 F77
1966 478M V6 WW 2483900 381167 23-184 HM/JM/TM/WM-8500 CK738 F77
1966 637 V8 WW 2492166 381177 ~ All-9500 F77

The above table was adapted from the excellent 60-66 GMC Truck Site at http://6066gmcguy.com