So...this will be my third teardown and rebuild of it, and after getting the correct airhorn on, it runs even better than before. Takes off like a bat out of hell and screams at full throttle! But of course...still running into idle problems (of a different sort this time).
This time I actually removed my old idle pickup tubes and carefully installed the new ones I received with my HP kit, making sure all passages were free and clear. My primary throttle shafts were already bushed, so along with bushing my secondaries, both shafts are freely rotating. There is a very slight amount of left-right play on the primaries when they are open, but they close snuggly and I tried my best to center them in front of a light. The only other thing I did regarding the throttle shafts was the fast idle cam piece (the one that is spring loaded onto the adjustment screw) was having some clearance issues with the throttle plates closed, causing it to stick, so I filed a bit of metal off of the piece so it would move more freely and let the throttle plates close fully without any hangups.
I actually got a hold of the Quadrajet Thexton tools and meticulously set everything to the proper stock settings using the tools (float, lean and rich stops, IAB, TPS). I set the idle mixtures screws to 3-3/8 turns out as per the instructions that came with the kit, tools, and my service manual. After warming up, I connected my dwell meter and found at stock settings the dwell was in the single digits, so per my manual I turned the IAB valve in until the dwell was fluctuating around 30 degrees, which did take several turns to get to, but never bottomed out. (Remember before with my old airhorn this was impossible, dwell was pegged at 54 no matter what!). Idle stop solenoid is set fairly low and engaging properly only when it should, so its not holding the throttle up. PCV is hooked up and functioning correctly. All vac ports hosed or properly capped. Still using the thicker airhorn gasket.
Now the main problem with the idle is that it is too high! Fully warmed up, choke properly open and fast idle disengaged, I get 1000-1100 in park and about 750 in drive. The throttle plates are fully closing, and the linkage is all the way against the idle adjustment screw (which is just barely sticking out of the hole as it is, where as before I actually had to turn it in to get the idle high enough to be smooth).
Some other symptoms: The dwell varied about 10 degrees with my air cleaner on and off ( I have the 14" edelbrock open air element with a wix filter). When I rev the motor in park, the rpms seems to be slow to drop back down to idle (the rpms drop to about 1500 and then slowly go back down from there, where as before it was almost an instant drop after releasing the pedal). Still getting what seems to be a slight backfire and idle and low part throttle. Sometimes get dieseling after shut off, which is expected I guess when the idle is too high?
Any suggestions on what's going on this time? Too rich? Too lean? I know a vacuum leak could be suspect, so I'm actually gonna go buy a propane bottle today and see what I find around the carb and intake manifold. Aside from that, any clues what I need to be looking for?
