Re: Rochester 4GC carb

Posted by Mike On 2011/8/24 8:16:26

From a hemmings article (FWIW):
"Earlier 4GC models were only available in 486, 553, or 692 CFM"

From a random internet forum post:

"Used on a variety of GM automobiles from 1952 to 1967, including the 1961 to 1963 Buick/Oldsmobile/Pontiac aluminum 215 V8's, the 4G was Rochester's first four barrel. Produced in 486, 553, and 692 CFM ratings, the 4G uses a squarebore layout with a conventional fixed jet, power valve and accelerator pump metering scheme."

And a size chart:

Model /CFM Venturi Diameter/ Bore Diameter

primary secondary / primary secondary


4 Jet/ 486 1 1/8 1 1/4 / 1 7/16 1 7/16

4 Jet/ 553 1 1/8 1 15/32 / 1 7/16 1 11/16

4 Jet/ 692 1 1/8 1 15/32 / 1 9/16 1 11/16


Hope that helps!