318 2bbl won't idle without choke

FYI
that carb can be idled all day with the top off, so long as the horseshoe clip is holding the float in place.

I have not had many factory SMB pumps, maybe a dozen, and only the 340 pumps occasionally make 6 psi. The others run 3.5 to 4.5

Like others have said, if the boosters are dribbling,the liquid level in the bowl is way to high; or the choke blade is bringing the manifold vacuum to the top.

FYI:
One other thing I discovered, is that the boosters don't care which way the air moves thru them, to flow. I had an engine once with a jumped timing chain, that only barely idled with the throttles wide open, and the ignition over-advanced. Air was actually being pumped backwards thru the carb, and a cloud of fuel was hovering above the airhorn. I was very young then, but it didn't take long to figure out something was seriously wrong!!
A similar thing can happen, at or close to fast-idle, if the intake valves, for whatever reason,are not fully closing. But in this case,if you open the throttle too far, she will start to send compressed mixture on fire, back into the intake. Which can/usually does pop up thru the carb. FYI