Engines Ruff idle ???????

[big.l.a]

I have a new problem with my truck after running hwy speeds and
come to a stop @ a light my engine Idles ruff (Shakes) but after
It cools down It runs fine. any Ideas as to what causes this.
It just start doing these about 2 weeks ago.

[LILREDGMC]

Sounds like something has changed. Go back to when it didn't exhibit this problem and make sure you didn't happen to make some changes. Then best I can offer is back to basics. Timing, dwell, advance, all vacumn lines: check the ends and cut back for better fit if necessary, what temperatures are you running, highway speed and when you get to the light. I had an old radiator that allowed me to run hotter than I should, until I put real gauge in I never would have known. There were subtle hints but no clear cut too hot message. When you say cools down, what are you implying, next startup its ok, or after in local traffic for a while its ok. Long distance trouble shooting is tough, on any equipment, especially if you can't hear, see, touch, adjust. Hope this gives you some ideas on a starting basis. Go back to the basics, the simple things and go towards the more complex.

[big.l.a]

When I say cool off I mean after setting for a couple hours.
I runs around 180 degrees @ Hyw speeds. I go over it and
check my timing It does seem to idle a bit high.

[68 with 350 TPI]

Check for a vaccum leak.

If you havent changed the carb or the timming that would be where I would start.

You can take a spray bottle with some watter and spray diffrent areas until you hear the idle change.
When it changes you probably found your leak.