Please... A short history...This is a 1978 F250 with the 300 inline 6 and a 1 barrel Carter carb. I use this truck primarily in the winter to plow. I recently fixed some fuel line issues and replaced the base gaskets on the carb, I also plugged 2 vacuum vents on the carb. I also set the heat riser choke so that it was open at about 65 degrees. The problem is that it runs too rich unless I keep the revs up. I can smell the richness of the fuel. What can I do to get this carb running nice and lean at idle? I vaguely recall reading something about vacuum having something to do with idle. There were also a couple of "extra" gaskets just beneath the carb which appeared to have passages that I simply plugged with Permatex #2. Was that my downfall? It runs OK now as long as I keep the revs up but I want to make it leaner so I don't have to keep feathering the throttle. Any experienced advice would be greatly appreciated. TIA,
Geoff

Geez I'm an Idiot!
After some screwing around I noticed while I was under the hood working the throttle that the air filter housing was getting sucked downward every time I gave it gas. Pulled the air filter and my problem went away. Who would ever have suspected a dirty air filter? Remember the K.I.S.S factor.

 

If it's running rich at idle, the mixture screw is probably too far out. A vacuum gauge is a handy tool to tune the idle mix. Connect a vacuum gauge to a manifold vacuum port (manifold vacuum is sourced below the throttle plates and is present at idle). Adjust the mixture screw until the needle reaches its maximum and is steady.

As far as the extra gaskets - it's a little unclear to me what exactly you did, but you never should use any kind of sealer around a vacuum passage. I'm not sure where you used it, so I can't say if that's the case here. In general though, carburetors never need any kind of sealer because (1) it's not really necessary and (2) sealant should stay away from areas of high vacuum.

 

When your engine is at full operating temp, pull your air cleaner off and make sure your choke is all the way open.