Charcoal can/vacuum/miss

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Re:'72 340 , thermoquad, Demon
Been fighting setting idle speed/timing/missing problem. Driving me nuts . Thought I might have a vacuum leak but found none. Had charcoal can purge line tee'd in pvc line to carb base. Removed purge line and capped ends. Was able to easier set idle speeds, and car ran much better. Still have a higher rpm miss (approx 4000 rpm) and need to recheck timing. Any thoughts on the miss ? Am thinking proper timing might correct it. Previously when trying to set idle/ timing rpms would shift higher and lower. As it did that the timing mark would shift also.
Charcoal can is off '73 Valient 6 cyl. and has 3 ports (tank ,carb bowl vent, purge). Guessing purge line was installed incorrectly creating vacuum loss. How should it be connected or will it just not work properly with this setup.
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[kiss]

The reason why the vacuum was easier to set was because you had the charcoal canister hooked up improperly. The charcoal canister purge port isn't supposed to be tee'd into the PCV line. It's supposed to be hooked-up to the purge port on your carburetor.

The purge port is a larger vacuum port that is ported vacuum, the same as your distributor advance port. The vacuum activates off-idle and is closed at idle. This is what you need for the purge port on the charcoal canister.

If your carburetor does not have a purge port what you need to do is tee the charcoal canister purge line into the PCV line with a vacuum-activated valve in between. NAPA Echlin # 2-28011. The valve needs to be teed into your ported vacuum line. That way when you step on the gas and go off-idle, the ported line will open the valve and allow the purge port to be sucked into the car via the PCV line.

EDIT:
Just some additional info, to identify the purge line on your carb, I forget the diameter, but it should be bigger than the normal little vacuum port, yet smaller than your PCV port.

What I did personally, since my charcoal canister was in bad shape, is I just removed it. I left the gas tank vent line sitting in the engine bay with a filter on the end of it, so it would at least have atmospheric vent. I've never had a problem with fumes or anything - I'm willing to be since the line is so long from the tank, plus the filter on the end, it barely vents anything at all out of the line.

 

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Vacuum purge valve should be here today. In your opinion where would be the best location to place it to help maintain the origional look of the engine compartment ? Are these valves directional in flow?
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[H22A4]

I mounted my purge valve between the back of the carb and the firewall. The vacuum source is off the vacuum advance and it's all hidden when the air cleaner is on. I'm using the power brake port on the back of my 1406 carb for the purge line off my charcoal canister.

You can just make out the top of the purge valve to the left of the vacuum advance pot in the picture below:

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[RustyRatRod]

Actually, the purge port on a Thermoquad has no vacuum at all. It is the large nipple on the passenger's side of the carburetor coming out of the float bowl. It is basically the float bowl vent. That is where the canister should be routed.

 

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Got purge valve installed before seeing RRRs reply so it is tee'd I to pvc hose. Installation smoothed idle rpm and timing mark staying steady now. Still have high rpm ( approx 4000) stuttering. Initial timing at 12' btc. I believe vac can is a 17' adjustable. Most all parts that I believe could be partially responsible for this stuttering have either been replaced or checked to the best of my knowledge.
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