86 350 Won't run
 

Hey thanks for the PCV info.
Fortunately down here in the South we ain’t go to worry about emissions, no smog checks here.

I’ve got a 81 GMC Sierra ½ Ton, with a 1986 350, HEI ignition, Rochester Q-jet M2ME, The other morning when I tried to start it, it was running really rough, once it got warm it seemed to be ok, but the next day it got worse….and so on until it wouldn’t even stay running, during this time, it was smoking a lot when I would accelerate, (Black smoke), When I crank it If I keep pumping it, it will stay running but just barely.
I have replaced all ignition components ( I was planning to do this anyway). But the problem didn’t go away, Its got to be the carb. I am thinking.
Its got good compression on all 8. Since I had to pull to dist. To replace the pick-up coil I have it static timed at 6 deg. Btdc, I can’t keep it running long enough to set the timing.
Any suggestions would be welcome.

try your choke.. and about the PCV, whether you have emissions or not. you still need the PCV!

carb is a M4ME not a M2ME
 

I made a mistake on the carb, its a M4ME

i had a problem like that with my 4.3 with the quadrajet now i had a PVC valve but im wondring if the carb is the problem, mine went through a rebuild which did little to help the problem cause the electric pump sensor ( not sure of its correct name) was the problem. I swapped out a different one and alls well now
hope that helps

have u tried adjusting the carb? theres 2 adjustment screws at the base on both corners, you'll need to pick up an adjustment tool to adjust those

You have the same problem as chevychic. The colder weather is affecting the operation of the carb. Set your choke to stay closed longer. I have the same problem. Once my truck reaches its operating temp of 180+ is runs okay.

Filled up with gas the other day, Blazer started idling rough, bad cat converter smell. Results of finding the best gas price. Next tank all was ok.

If you have a black electrical plug going into the top of that carb. then you have a "electronic" Q-Jet.
It has a mixture control soleniod under that plug and they often go out and cause the type of problems you are describing.

I would fix it by putting on a Holley 650 Vac. secondary.