I have a 1993 1/2 ton. Just put in a rebuilt 350 (1978 rebuilt bottom end with 1993 top end). I am having a timing issue. The motor will run okay going down the road, however, while in gear at a light it will idle smooth for a minute then start to miss and eventually cut out. Is it possible for the distributor to be off by one tooth?

 

Sounds like a vacuum problem. At any rate get a vacuum gauge and see if you can identify what's going on. There are some great info on the net for identifying engine problems with a vacuum gauge. See THIS article.

Another Article.

Almost forgot..to check for vacuum leaks use a spray carb cleaner and listen for changes in RPM.

 

slw210: I checked the vacuum as suggested, no change in RPM. I got the motor to #1 TDC and adjusted the distributer again. The motor seems to be running alot better once it is warm, however, when it is cold it lopes between 400-950 RPMs. I'm thinking that since its a new setup in the truck I may just need to drive it awhile to work the bugs out or hear anything back from the forum. Thanks for the help.