I am installing a factory Vr57 blower on my 57 312 retractable, am keeping OEM as possible, but would like to keep the factory carter AFB the  engine came with as it works so well. any modifications or does or do-nots that any one can relate will be very helpful.

I run a late model Edelbrock 600 on mine. Works very well. I would suggest you purchase one of them and save the AFB for use on an unblown engine. It will look the same, but work much better.

Frank/Rebop

Bristol, In ( by Elkhart) 

I ran the Edelbrock 1405 (manual choke, 600 cfm) for years on my 'bird, with an SN 2000. Just changed the accelerator pump to the marine version. The Studie guys told me they'd go 12 lbs boost with no other mod. I only ran 5. Worked fine,never any sign of fuel leakage around the shafts.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

The 1957 Carter carb secondary diaphragm is outside the carburetor with the boosted air supply simply being supplied to the carb interior via a bonnet.  The secondary diaphragm is not being externally pressurized and is therefore not 'boost referenced'.  Because of this, the spring side of the diaphragm is under boost pressure rather than being in a position to have a negative pressure signal being applied to it.  For this reason, unless you can pressurize the outside of the secondary diaphragm on the 1957 Carter carb, the secondaries will not open.  Frank and Mikers both have the more modern Carter/Edelbrock carb and works in a blower application simply because the secondaries have an internal weighted valve above the fuel discharge nozzles which is within the confines of the portion of the carb being boosted. 

Lorena, Texas (South of Waco)