ok guys i need some ideas, i bought this truck because it is rust free, and in indiana, that is a good thing. ok when i got it it had blow by, bad. so i got another 4.9, paid a friend to install it, he kept the intake ex, and carb, with the truck and put them on the new motor. when he was done instelling it, it ran rough, but did not smoke, or have blow by, but was loading up. i put about 200 miles on it, and it started to smoke a little, and smelled like raw gas, we put on a new carb yesterday, when it started it ran good for about 3 minutes, then it started to load up and run like before. my question is is it posible that something is plugged in the manifold? motor is not breathing? sorry this is so long, but wanted to tell what i know. any ideas from you guys is welcome. thank you jim

 

What do you mean by "loading up" and how are you measuring/IDing it? It sounds like the timing or mixture is wrong. Read this page & the next:
http://www.users.bigpond.com/ergoff/vac1.htm