Purchased a running 68 350 six months ago and between doing a lot of refinishing and replacing on all aspects, I am now attempting to tune the car.
The other day I replaced all plugs (AC Delco 45S gap .035), plug wires, fuel filter, dist cap, and points.
I set the dwell (before anyone asks yes...with a dwell meter) @ 30 deg, and timing at 9 deg BTDC and vac advance disconnected. I had the car running for about 15 minutes while tuning it and dialed it in to 800 RPM. Engine was running smooth and went ahead and set the choke wide open. Was running great!
Let the car sit for about 5 minutes and fired it back up and the idle is horrible! The car does not seem to want to hold an idle.
Timing and dwell are still the same and timing is not jumping around. Replaced Vac lines and didn't seem to make a difference. I have the choke wide open and if I put my hand over the choke the idle steps up and the car runs lean. Temp was normal and no odd issues or noises. Double checked intake bolts, carb hold down bolts, plug wire routing, etc

I have a stock 350 WC code engine and a 4 speed. I purchased the car thru an estate sale and have some documentation on a complete engine rebuild, but the car had a 73 4 barrel carb (q-jet) and a 74 intake(EGR blocked off) I pulled the intake and replaced it with a Edelbrock performer (non-EGR) I don't have any vac ports on the intake (all plugged with exception of PVC) as its a manual-non power brake car and I have the Vac advance on distributor going to back of the carb.

I went thru the carb to make sure everything is good and jets-needle are fine. Accelerator pump works fine, float is where it needs to be, no clogs, gunk, or bad gaskets. I did find out my Jets are 72's and Metering rod 41.

Going to bolt the carb back on and put a vac port on the intake an get vac readings on everything tonight...
Any suggestions or something I am missing?

Sounds like after it cooled down it developed a vacuum leak somewhere. Get some spray WD40 and start looking.

Thinking vaccum leak or possibilty that vaccum advance in the distributor failed.

I think someone posted this earlier, but it's worth posting again. Great resource for using a vacuum guage!

http://www.secondchancegarage.com/public/186.cfm

Update:

Bolted carb back on and put on a thicker carb base gasket. Double checked all plug wires, vac lines, and linkage.
Since I have a edelbrock performer intake, double checked intake bolts and since I don't have a choke on my intake, I have the choke locked open

The car runs like hell until it gets to about 160. I sprayed all areas of the intake and vacuum hoses with WD40 and no change. I sprayed some carb cleaner and I have a leak at the front of the carb on the passenger side at the base. Also at choppy idle if I spray carb cleaner on the secondaries, the idle smooths out ( but secondaries are closed.
Double checked my vac advance, distributor, and wires ( all fine )
Checked vaccum at carb and intake and both are fine

Now question #1 : Do I need an adapter for the intake with running a 74 quadrajet? Looking at my old intake, the ports for the primaries a d secondaries are closed off...the edelbrock is a Spread Bore.

Question #2 : I can understand the vac leak at the base...but what about the secondaries? If i just spray a little bit of carb cleaner, the idle is fine
Again, what am I missing?
Thanks in advance!

Are you sure the intake gaskets and the heat crossover ports are matched up. There a gap issue with newer intakes and older heads.

Did you check the Q jet for straightness, sounds like the throttle body or Float bowl is warped?
Primary Shaft leaking? loose, All easily fixed.
No you do not need an adapter, I am also going through this too, mine was warped and lots of leaks. I had to unwarp it then find and correct any mistakes I had made.
I found I had set the throttle plates off, shafts were binding plates not closing.
You also need to choke her til it gets up to temp.

I was told by the Carb Shop in MO to trash the Edelbrock Performer Manifold and use a 1968 Q jet stock cast manifold, I have since removed the Eddy.
Now I am learning how to setup and get the Q jet right for my setup and I understand that I will never go back to a Carter/Edelbrock once I get it right, I am so close.

Yeah, this is turning into a bigger PITA than I thought. I put a new performer intake on because previous owner had a EGR manifold that had the ports closed with JB weld or who knows....
Going to pull the carb again and double check everything again...worst case I see a new carb in my future

I was just talking with a local engine builder the other day and he had nothing good to say about new edel intakes. Of course most of his issues are with chevys but he says he has had so many that are cut at the wrong angle and don't seal against the heads that he won't even put one on now unless he runs it across a mill first to straighten it out.

Tom the link didn't work for me, just me?

http://www.secondchancegarage.com/public/186.cfm

Try this