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Yes you did, and I was reading the carb port just to verify if the idle holes were still uncovered after I redid the lean-best idle procedure. At 1 1/2 turns (and 2 1/4 turns out on the mixture screw) the engine only idles at ~650 (vacuum at <1"). To increase idle rpm to ~850 and smooth it out requires 2 turns in, which then increases the vacuum to 4".
The manifold vacuum is another issue. With the carb port blocked (and both distributor ports blocked), manifold vacuum flutters between 16" - 20". Turning the idle screw in another 1/4 turn (now at 2 1/4 turns) the rpm increases to ~1000, vacuum holds steady at 21", but the carb port vacuum also increases.
So isolating the carb from both distributor diaphragms seems to indicate the vacuum leak is at the carb, or even the brake booster as Opelbits mentioned.
As I understand, I'm shooting for ~850 idle rpm (warm, choke off), 0" carb vacuum, and ~20" manifold vacuum. Is that about right?
Not so uncommon in my experience. That’s about where mine sits with zero vacuum at the port at 3° of ignition timing with things set up properly. I’ve done backflips trying to figure out why. I got away with what you’re doing on my old 1.9, no problem other than the occasional feathering on the gas pedal off idle due to periodic off idle stumble.

Since my 2.0 doesn’t like it and diesels upon shutting down the engine I’ve been pushed into better habits and I must say it’s paid off. I have it set up by the book now and by doing so all but eliminated the off idle stumble and moves through the progression stage much better. I had to modify the distributor by limiting my mechanical advance so I can get it to idle at 850 rpms,14° at idle gets it there, no less.

Your manifold vacuum sounds healthy, at 850-900 rpms my old 1.9 pulled 17”, my recently built 2.0 pulls just over 18”, raising the rpms boosts it up to 21”. I consider that healthy.

Keep up the good work.
Can you describe how you seem to be running too rich? How is the gas mileage?
 

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Discussion Starter · #22 ·
I haven't been tracking the mileage. The indicators of running rich are black soot blown out the tailpipe at startup and the spark plugs were sooty. Plus it smells rich at idle. Otherwise the engine idles nicely at 850 and the car drives fine.
Aside from this, last weekend I installed a new drivers-side linkage grommet; the old one had disintegrated. Since the linkage had to be disconnected anyway, I removed it all and cleaned it up and greased the ball & sockets.
I'm going to keep fiddling with the vacuum while search for a canister. Your input and the others have given me a much better understanding of what to diagnose. This weekend I'm going to pull the airhorn again and look at the power valve.
 

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Detritus Maximus
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If it's running decently, I would say the power valve is fine. Maybe see if there is any crud in the valve in the bottom of the fuel bowl. It might be leaking a little there.
 
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enjoy your vacation well deserved I'm sure
 
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