Anybody know what cfm the 4GC on a 1966 429 caddy is? Tag number is 7020603, if i remember. Just curious. Thanks -ace
7026030 stolen from another website: 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. Secondaries are mechanically actuated but use an adjustable spring loaded air valve. Adjustment is achieved by loosening an allen head set screw and inserting a screwdriver. Rotating the screwdriver counterclockwise increases tension. The accelerator pump is also adjustable, using a link with 5 adjustment holes. Four center pivot floats are used. The 4G's used the small diameter 4-7/32" diameter air cleaner, shared by the first generation Carter AFB's, so the usual aftermarket air filter cases will not fit. However there are adapter rings and street rod sources usually carry compatible air filter cases. While the Rochester book mentioned in the reference section briefly covers the 4G, your best bet for information is a GM shop manual from the '50's or '60's. 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 If you can get an older copy of the Doug Roe book on Rochester Carburetors, it has a pretty good section on the 4G. If you need an air filter adapter for the 4G, the Mr.Gasket pn is 2082, to use a standard 5-1/8" filter base.
yeah, i found that thread the other night too. I just put the carb on the car already, and its running great. i don't feel like taking it back off to measure Just wondering if anyone knew off top of their head what it might be. thanks for the repsonse Treb11 -ace
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