Rough idle 1981 B2000

Vacuum lines replaced. Check... Clean fuel, new fuel filters. Check. All ignition/spark. Check. A short history.. Truck sat 3 years in Mesa, Az. I've replaced all vacuum lines, all electrical checks out, as well as fuel feed. I'm still getting a rough idle. Would a timing adjustment be needed? Truck starts just fine, idles a little rough, and bogs down under load. I've done plenty of engine work in the past, but I'm miffed.

It's the carburetor jets...

Thanks, norwoodn. I'm going to get in there and check that out.

Should I presume the carb will need to be removed to clean the jets? If that's the case, I may as well do a complete rebuild. Gotta learn some time. ;)

Pretty much. Take pictures as you go, and let us know what you find. And we all can learn from your clogged jets.

Added note: The truck was in Mesa, AZ, an altitude of 1,240ft. Now in northern AZ at an altitude of 4,707ft. How much effect would this have on how it runs?

Dogfather - my 1988 B2200 and my 1971 VW are both carbureted (Weber aftermarket carb on each), and I never have had any issues whether in Phoenix, Prescott (5000 ft), or even in Flagstaff (7000 ft) with those. At most you would need to use a slightly smaller main jet or idle jet/leaner idle mixture to compensate for less dense air. If you're going to try the idle mixture screw, write down how many half turns you do turn it, so you could go back if necessary; and only adjust once engine is at operating temperature.

Is the choke hooked up and working?

Thanks, Cusser. I don't recall having issued with my old Busses, but both carbs were stock.

Choke is hooked up, I'll fire her up and check that to make sure. The carb is a re manufactured Holley. Follow up with adjusting idle mixture.

No change other than bringing down to almost stalling. In another round of line inspection, I discovered the hard line from the valve cover to the manifold was cracked. So brittle, when I went to disconnect it, it broke on half. I imagine years of the Mesa , AZ heat takes it's toll.

I do need to mention all smog has been removed. No pump, no rail on exhaust manifold (bolted off). Catalytic converter is still intact. Is it worth checking the timing? Would it really need it from sitting idle for 3 years?

That has electronic ignition, right? Then timing should not change unless distributor was removed or rotated.