first the easy one. there's a nipple coming out the primary metering block, I'm not sure what this is for, looks like a air line or may a gas return line???

second one may be a little harder. when rebuilding the carb I ended up changing the check valves in the pumper housings. the old ones where the the metal ball with the strip of metal holding them in. the new style was the rubber umbrellas, but now the pumper levers are slow to come back out and I'm afraid that they're not going to be back in place before the first to second shift at the track. is there anyway I can test the system with out filling the bowls with gas I.E. using something other than gas or just filling the pumper bowls or does it need the pressure of properally set fuel levels? I just don't want to waste gas and I can see a big puddel of gas on the ground if I try filling the carb up with gas.

 

The nipple coming out of the primary metering block is "timed" or "ported" vacuum. It is above the throttle blade at idle so it doesn't get vacuum until the throttle is partially opened.

What is the "List" number of this carb?

 

part number is 4776-2. thanks for answering the first one, that makes total sense now. I looked all over the internet for a diagram and had no luck, but it's kind of hard when you type in holley thingamjigger.

 

any thoughts on the second part?