[Dee]

You may find that a water heated carb spacer ( '60's Ford) will improve performance on the low end. It will also have a port for a PCV system and help eliminate any icing tendencies. I have 2 Zephyr engines using single plane open plenum 4 barrel manifolds. One engine stock and one modified and they both idle fine with using the smaller Autolite 4100 carburetors.