The amount of fuel pressure a carburetor can accept is defined by:
(1) The buoyancy of the float
(2) The placement of the float pin
(3) The orifice size of the fuel valve seat
Carter used at least different volume (read buoyancy) floats in the various AFB four-barrel carbs (505 different).
By using the float with the largest volume, and a slightly smaller than stock (I cut my own) fuel valve orifice, I have no pressure issues.
Jon
Thank you for that clear explanation. Recently, I cleaned up a Holley 4 barrel carb. I bought this carb brand new many years ago. When I removed the float bowls I was surprised to see that the floats were different. The primary has a plastic float and the secondary has a foam float. Valves look interchangeable.
