Can I disable the secondaries on a dual carb AFB set up? My search is on for the right set of carbs so my coupe is parked, however I have two good 650 AFBs on the bench, way too much for my 311 CI Chevy. I was curious about blocking the secondary areas with a restrictor plate (and removing butterflies) and plugging the secondary jets and just running off the primaries. I’m not sure if there is any other passages or possible? Or... since I'm running a Bob Creitz open plenum intake would it be ok to run a single working carb on the rear and keep but block the front? Remember this is temporary to get me going for a couple months.
Just block the rear air valve from opening. If it doesn't open you won't get any fuel (or very little) through the secondary venturii's even if the rear throttle plates are open. Another option is to use the lock-out that already exists in the choke linkage. You would probably have to modify it some.
If genuine Carter AFB's: From the passenger side of the carb: (1) Remove two hairpins on the "L" shaped link connecting the primary throttle arm to the secondary throttle arm (2) Remove the L-shaped link (3) Place the link and hairpins in a zip-lock bag (4) Place the zip-lock bag in a larger zip-lock bag (5) Place the larger zip-lock bag in a manila envelope with appropriate writing. (6) Seal the envelope (7) Give the sealed envelope to your wife (or significant other) for safekeeping Takes longer to describe than to do. Oh, and a few of the originals have flat washers on the link. If present, obviously remove them as well. For 311 CID, a pair of Carter 4758s AFB's or a 4758s rear, and 4761 front (chokeless), would make a good combination. If the engine is basically stock, then a pair of 9400s or 9410s would be even better. Jon.
Thanks guys! CARBKING may have seen my work before, as I get older step number 7 applies more and more! I like your recommendation on the Carters. The early tall top AFB's appeal to me and would like to talk to you about putting a pair together.
This is probably not the best idea,,,,,forgive me if I’m wrong . But aren’t they vacuum secondary? They will only open any at all,,,,if the engine needs it right ? Tommy
This would depend on WHICH AFB. The angle of attack on some of the auxiliary air valves is such that there would be air flow if the secondary throttle plates were open. And many of the Chrysler AFB's were NOT vacuum dependent, as they omitted the auxiliary air valves entirely. Jon.
Carbking Could you tell me what CFM I have on my 327/300 hp the # 3721SB TIA Just my 3.5 cents Live Long & Die a Fool
Carter published a figure of 575 CFM for this carburetor. This is one of only a very few O.E. AFB's with published CFM ratings. Jon.
Back when,I ran a 301 sbc with two 650's step the jets down and metering rods,will be just fine to drive around.
The Jalopy Journal
