Truck is not running

[Kip7143]

Hi Guys!

I am hoping for some help with my 1981 Chev. Since I bought the truck it's been a little rough and tempermental but drivable for the most part. Now it's really not running. So here are some details.

The truck at this point is only running when throttle is held. As soon as I get off the throttle it chokes and dies. When it is running, its sputtering, almost like a misfire. Since I got the truck I knew a lot of the vacuum lines were old and cracked, so I recently replaced everything to see if that made a fix.

Still the truck isnt idling and will only run on throttle, with a good sputter. Does anyone have any idea where I should start? One thing, when I disconnect the vacuum from distributor it still runs very rough, but wont stall.

Second to all of this... I do not know how to time this truck. There doesn't seem to be a timing tab.. does anyone know how to time the straight six motors?

NOTE: the clip is from a 79, its not the factory clip on that truck

1981 Chev C10, straight 6 4.8l motor, Automatic. Pretty well all stock.