Well, I'm considering rebuilding my holley 4165 (650 double pumper spread bore quadra-jet drop in w/ mech secondaried), though I'm not sure if it's worth keeping. The engine idles fine(~800 rpm) now, but the only problem I have is the engine sputters when flooring from a roll, and will just plain die if you're at a stand still. This is not an instant thing, I usually have to keep it floored for 3 or 4 seconds for the engine to completely die. I have a vacuum gauged hooked up to a manifold vacuum on the carburetor, and when I floor it it goes down to ~1 inHg. I'm guessing this means that the engine is getting too much air. I have a real q-jet that I used for a couple months just to get the engine running, and it still kind of sputtered but not quite so bad, so I'm thinking there's something wrong with the tuning. Anyone have an idea or have a problem like this?

 

Where do you have it plugged in? You should measure vacuum at idle, not at WOT. Manifold vacuum is created when a piston moves down in its bore. It creates a partial vacuum that pulls the air/fuel mixture from the intake to the cylider. The vacuum part is created by the resistance from the throttle blades. The more they are closed, the more resistance, hence higher readings. The further they are open, the less resistance so naturally, the lower the reading. So, like said, measure the vacuum at idle and make sure it is plugged to a manifold vacuum source.

The problem sounds fuel related. Perhaps the floats are set wrong and you are sucking them dry. Perhaps you have a dirty fuel delivery system. What is the fuel pressure to the carb?

 

If it USED TO run well but doesn't now then something has gotten screwy inside the carb. Something clogged up, jammed, bent, cracked or whatever. Since it takes a while to die after being floored I'd say something is clogged up, perhaps on the secondary side of the carb, preventing fuel flow from keeping up with the air that's being admitted the instant you smack the throttle wide open.

You're PARTIALLY right- too much air. Really, air is going to flow as much as the engine can handle as soon as you floor it (and the throttles open up). But the carb isn't doing it's main job properly- MATCHING that airflow with the correct amount of fuel.

 

I'm running at about ~4.5 psi fuel pressure(I have a gauge hooked up to that too). The manifold vacuum is running constant at about 18 inHg during idle. It's almost as if the engine is sputtering. I just went out and tried this. I've been working on transmission and rear end so the car is competely off the ground, so the back wheels can spin freely(I know it's cheesy, but a easy way to go through the gears and make sure everything is working right). When I floor it for a second until the engine starts to die and let up a little bit(to about 3/4 throttle), the engine starts throttling up and it takes off. I have a brand new o2 sensor on the original exhaust for the v6...could I just rig that up on one of the tailpipes and just hook a volt meter up to it to find out if I'm lean or rich?