Panic - I do not have one to look at, what size are the primary throttle bores/primary venturii on the Holley 390?
The small Carter AFB has a throttle bore of 1 7/16, and a primary venturi of 1 1/16 inches.
For comparison, the Pontiac Sprint Q-Jets (which are available) have the same 1 1/16 venturi, but the throttle bore is slightly smaller at 1 3/8 inches.
No argument, just would like to have the specs for all in the same spot.
You nailed the biggest issue with the Sprint carb, being the lack of an intake.
EDIT: for additional comparison, the primary venturi on the 265 CID Chevy WCFB is also 1 1/16 inch; while this was increase to 1 1/8 inch for the 283 CID Chevy.
Jon
Best I can tell from this Holley chart:
The 390 cfm 4 barrel (both 4150 and 4160 configurations) has:
1 - 7/16 primary throttle bore
1 - 1/16 primary venturii
