Toll free 1-888-664-6462   doc@carbdoc.com

Rochester Model B Carburetors

Model B History and Identification

Early Rochester Model B Carburetor

1st Design Model B Manual Choke Carburetor, 1950-51 Models (10-32 Airhorn Screws) Clamp-On Oil Bath Air Cleaner

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)

Rochester Model B - Manual Choke

1st Design Model B Manual Choke Carburetor, 1950-51 Models (10-32 Airhorn Screws) Clamp-On Oil Bath Air Cleaner

Rochester BC Carburetor

2nd Design Automatic Choke Carburetor Model BC With Wing Nut Air Cleaner Attachment (1957-up)

Rochester BV Carburetor

2nd Design Automatic Choke Carburetor, Model BV, 1963-up

Rochester B Slotted Type Pump

1st Design Pump – Slotted Stem, Leather Cup

Rochester B Round Stem Pump

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 early 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
standard kit CK10 CK10 CK33 CK31
master kit MK10A MK10B MK33 MK31

The Carburetor Doctor