This car has been doing this for a while. It doesn't matter if the engine is warm, cold, driving or starting at a dead stop. When I floor it, the rpms drop and I think that it will stall then it revs up. I just swapped the motor so I did all of the new plugs, rotor, cap, wires, etc. I will change the fuel filter tonight, but I don't have much hope for that. Can you guys give me some ideas of where to look? Is this a carb problem? I'll pull some plugs and see if I can tell anything obvious from discoloration.
The car has a 350 truck motor, Hedman headers, summit aluminum intake, Accel header plugs, OEM type wires ( I know), and the rest is stock. rochester 4bbl carb (I have a spare that doesn't create this problem if I remember correctly, but the TPS is bad)

 

Sounds like your secondaries are leaning the motor out. try going up a few sizes with your squirters

 

"Quadrabog".

First, make sure your timing is set correctly. Are you disconnecting the EST wire (computer controlled) or vacuum advance (non-computer controlled) when you set it?

Then, go to the tech articles linked from the thirdgen.org homepage, look for the one on "tuning for performance with your computer controlled quadrajet", the section on setting the AV. Don't worry if your's isn't computer controlled (since you mentioned TPS on your spare carb, I assume it is), this issue is the same regardless if computer or non computer controlled.

The only thing the tech article doesn't cover is the choke pull-off - if it's leaking, you'll bog.

 

choke pull-off is good, I replaced it about 6-months ago and it works well now. I've been trying to tension up the secondaries. This seems to work for a while (2 or 3 days) then the problem starts again. I haven't tightened the set screw underneath the spring tensioner screw because I rounded out the head. I guess that could be the problem.
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I forgot. The timing is good, I set it correctly. And the q-jet is cc.

 

If you can't tighten the AV tension spring set screw, the AV will not have proper tension. Without proper tension, the AV will flop open earlier than it should, which will cause a bog.

You can't check the choke pull-off while watching the engine run. The engine will produce enough vacuum to pull it even with a leak. The proper way to test it is with a vacuum pump like a Mity Vac.

 

You can just push the vacuum can shut, and block the hole with your finger. If it just leaks out, it's done. If it stays closed, then it's fine.
If it's that new, it's probably fine.

Sounds like you already found your problem, the rounded nut.
Try and remove it, and bring it into a bolt supply store. It's something like a #4 set-screw, about 3/8" long or something.

 

I got the secondary problem fixed. There was an improvement, but the problem isn't solved yet. The engine doesn't fall flat on its face any more, but when I nail the gas I can here tapping and and the engine reves and dropps revs and drops then revs. There isn't much power left in it when it finally revs. when the gear changes, i get the rev and drop thing all over. Is there a bad lobe on my cam shaft? Misfire? where do I start looking now?

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oh yeah, Ichecked the choke pulloff with a mightyvac. It holds vacuum just fine. I couldn't detect any leakage

 

Any ideas? Is the camshaft idea even possible? Would it cause a problem like this? The only reason that I think cam shaft or valve train is the tapping symptom. The rpm changes are fairly smooth, quick, but smooth. usually a misfire would be more jerky right?

 

I got the "tapping" problem fixed. Turns out that I blew the exhaust manifold gasket apart at cylinder #7. I've been working on the secondaries which I'm 99% sure is my problem. I kinda lost my ***** to get on it when I heard really loud tapping. Funny how that happens.