Someone swapped a 1954 passenger car engine into my 1948 Chevy 3100 prior to me acquiring it. I'm trying to identify the carburetor it has so I can order a rebuild kit, because the carb is leaking and I have a tip-in hesitation issue (like the accelerator pump is not working properly). It looks like the GM Model "B" Carburetor shown in the 1948-53 shop manual, but the shop manual doesn't mention that the Model B carb even has an accelerator pump.
See attached pics.
1948 Chevy 3100 Thriftmaster pickup Old skool engine swap ('54 pass 235) Four on the floor 12v conversion
Check out this Engine Shop Tech Tip on Rochester B Identification. Your carb certainly looks like a Rochester B. Once you remove the carb, look at the underside of the throttle body for a stamped number (if none stamped look along the base flange edge for a cast number) and the underside of the main body fuel bowl for a casting number. You can compare your numbers with the ones in the Tech Tip to hopefully ID your carb and get the correct rebuild kit.
My 1948-51 w/1952 Supplement Shop Manual describes what most folks call the "accelerator pump" as the "Pump System". Same thing, just different terminology.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
7004497 is the casting number on the float bowl of mine. Which seems to indicate it is a 1951 235 A/T carb. What's the difference between an A/T and S/T carb?
Last edited by SinisterPerf; 09/21/202412:10 AM. Reason: added info
1948 Chevy 3100 Thriftmaster pickup Old skool engine swap ('54 pass 235) Four on the floor 12v conversion
A/T = Automatic Trans - S/T = Standard (Manual) Trans
According to carbking’s Rochester B common identification list, 7004497 was the bowl casting for multiple application carbs. That includes a 1952 truck with 235 and 1953-58 trucks with 235, most of those would have had a manual transmission.
Did you find a stamping on the underside of the throttle body or a casting number on the edge of the throttle body base? That will help ID your carb hopefully.
Last edited by Gdads51; 09/21/202412:51 AM. Reason: Add detail
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
FYI, judging by the pictures, I would have a look at that air cleaner. If it is an oil bath type, check for a crack somewhere. It could be leaking oil into the engine and may cause running issues.
There is very excellent information on this forum for refurbing the Rochester B and BC. Things like check for warping of the fuel bowl and airhorn before buying a rebuild kit.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
