Needle and seat info needed

[Mr.Pontiac]

I am noticing lately a lot of carbs. Showing up with 4 cut-outs on top of seats and not 2 non window design, I make my own after redrilling and testing them with a vacum tester. Any differance I should know about the 4 cut ones instead of 2? I know I’ll get the right answer here.

[Cliff Ruggles]

I would NOT use N/S assemblies unless they are the solid variety.  The ones with the cut outs or drilled holes allow the carb to drain back too far after a shut-down......

[Kenth]

I have found that using a mech fuel pump with a check valve, regardless of the type of inlet valve, does not "drain back".
The reason why the fuel disappears from the float bowl after the car has been standing for a few days is evaporation of the volatile fuel into the atmosphere.
Using an electric fuel pump w/o anti-drainback valve a solid inlet valve may delay the evaporation some, but with an electric fuel pump you can prime the carb ahead of "start". Again style of inlet valve does not matter.
I too prefer the solid style as Pontiac/Rochester found they provide better "fuel control" in the float bowl.
Pic from 1978 Pontiac Service Manual:

[Cliff Ruggles]

I'll add here that fuel pressure above the inlet needle is ZERO.  If you ever have the top off of a Q-jet with an electric pump feeding it and hold the hinge pin down you can push the float down and observe how the bowl fills.  It doesn't spray all over the place like one would think.  Filling is smooth and steady but also very quick to respond to float changes and the slightest movement of the float instantly keep the fuel level in exactly the same place.

As mentioned ALWAYS use the solid fuel inlet seat.  It's not a perfect World out there and the carb sits higher than the fuel tank in almost all of these set-ups.  The solid seat prevents any drain back in the bowl even if a return line is being used, and probably why they went to solid versions in later years.

I still hear folks regurgitate inaccurate information that the "windowed" variety are for "high flow" or "high performance", neither of which is true.  I've dyno and drag strip tested solid and windowed N/S assemblies and not one ounce of difference anyplace......FWIW.....