Nit Picking and Just Curious

[texasmike]

Some of you will think I'm just anal but being retired, with ample time on my hands, I just want everything operating the way it was designed to, or better.
So here's the latest: I've recently noticed that after running an errand, when I return to the truck and start it, I see a puff of black smoke at the exhaust pipe. After revving it two or three times, it clears up and doesn't happen again until the next time I shut it off and restart it. It always starts quick, idles smooth and runs great. When I open up the secondaries, no smoke of any kind is noticed. The air/fuel screws are adjusted to max manifold pressure (19.5") and are about 3/4 turns out. After the truck sits for an extended length of time, like overnight, there is no smoke on startup. Could the carburetor be dumping fuel into the manifold when I shut it down but after sitting long enough, the fuel has time to vaporize and evaporate so no smoke on startup. Any ideas out there on what may be causing this?
The truck gets a LOT of attention in parking lots and I would rather not have the black cloud around it when I leave. Is that being too self conscious or anal?

 

[Copymutt]

Typical fuel boils in the bowl after you stop, drops into the intake. When it gets bad you’ll need to hold the pedal to the metal & crank longer than needed to dry it out. Beyond the basics of float properly adjusted, phenolic carb spacer may block the heat transfer from the heads. It’s worse w/ ethanol.

 

[fast 99]

Same issue, it is actually rather normal. Even back when we had decent [higher octane] fuel designed for carbs it was a problem on hot days. Especially when heat soaked. E-free will help along with the suggested spacer.