Poor performance after engine rebuild

[Nikkortim]

I’ve been reading several posts about poor gas mileage, and have a similar problem.

A friend has rebuilt a ’80 350 and replaced it for the 350 in my ’85 Silverado.

He used the intake manifold and Q-Jet, and HEI distributor from my ’85.

The engine would not start until we bypassed the ESC by jumping two wires together, (thanks guys).

While driving it home in rural South Dakota I could see the fuel fall very fast, and it used a quarter tank in 25 miles, but the bad part came when I was going up a hill. I was losing speed and gave a bit more gas, then it start running bad, and shuttering, and my wife said it blew out some smoke , (about the time I punched it). I had the pedal almost all the way to the floor and could barely maintain 55 mph.

It stalled when I got to a stop sign, and I had to push the pedal all the way in to restart it. When I got to my next stop I down shifted and brought the revs up. To my surprise it began running smooth again so once I got into town it stayed running all the way home.

Since it sat for almost 4 years I’m going to say I have an issue with the carb even though my friend says he “knows” the Q-Jet. I also have the “Choke” light coming on in the dash, but I don’t know if this is because he did not connect it or the choke stayed closed. I’m not 100% certain about how it was timed. I am not certain if what we did to the distributor is the correct thing to do, or if I should replace it with a MSD HEI.

I also have a not related issue of a hissing (vacuum) sound when I depress the brake pedal. I have been told it is vacuum boost for the brakes, yet they work ok. Would this vacuum issue also be related to any vacuum issue with the timing or operation of the Q-Jet?

As long I have a good block and new exhaust now I guess all the other items I might need to work on should not be that hard for me now, I just need a bit cash and time.

I open for suggestions. Thanks in advance.