i have a 78 f150 .when i first start it up it runs pretty good . but when i drive it for 2or3 min it acts like it is out of gas and shuts off .it will not start again for hours . dont have any idea what it could be .. any ideas

all the normal questions...

has it still got spark,

has it still got fuel getting to it,

etc ??

Sounds to me like the dizzy is getting hot and playing up. Electronics have a nasty habit of doing this.

yep had the exactly the same problem on my 6 cyl falcon, it would drive like a charm and once it got hot (ie 20 minutes on the freeway) it would just stall and that was the end of it, but for some reason the next morning after i got it towed home (several times) it would start first time and be fine.
The problem with it is the module inside the dizzy is rooted and when it gets a bit of heat to it, it craps itself and doesnt function. probably cost around the 50- 100 dollar mark for a newy. This should fix ya problems.
Cheers John

Also if you are putting a new one in it, make sure you put some of that heat paste on it (like the stuff they put on CPU chips in computers) it usually helps it out a lot.

Ummm, why would you put heat sink compound on it ??? What this goo does is helps transfer of heat from an IC into the heatsink that it's bolted too. Covering something in this goo that is directly air cooled wont do anything.

If these dizzy modules have heat sinks then go ahead, put it on the mating surface. But AFAIK they don't.