Carb help

[79K20]

Hey guys-

Just looking into tuning the carb on my truck and, frankly, I am not sure where to start. Truck is a '79 Scottsdale K20, 4x4, with a 350 4-barrel and a SM465 4-speed trans. As far as I know, the carb is original.

The carb is (I think) a Rochester Q-jet. I am looking to adjust it because it hesitates slightly in low RPMs. Anybody have a how-to for these old carbs? I've owned a bunch of Holleys and an Edelbrock, but never a Q-jet. Any help would be appreciated.

Oh, yeah, I am in Denver at ~6,000 ft, so the tune will be much different that you sea-level guys. Thanks!

[gold84gmc]

i dont know how to adjust it but with the hesitating...check your fuel filter...mine was doing the same thing and the fuel filter was dirty so i replaced that and it fixed the problem

[DnStClr]

I would get a can of carb cleaner and get to work cleaning that carb. Your throttle plates look like they are good candidates for sticking. There have been a bunch of posts for Quadrajets. Do a search for Rochester Quadrajets. You can get rebuild kits for them.

[Dragon]

DnStClr is Correct, get to cleaning that Poor Ol' Quadra-Bowl(Big Mouth 4 Barrel that likes to suck gas, when it looks in that bad of shape), and do a Full Rebuild on it....  Adjusting it won't get you anywhere near where it should be, after it has been properly rebuilt (They are some of the easiest Carbs to Rebuild, its just getting the float at the proper setting that takes patience)......

Yes there is adifferent adjustment for a "High Altitude" and "Low Altitude" Carb, so if you try driving a Vehicle with the incorrect adjustment, it would be like it was sucking a through a stir-stick straw, rather than a good sized regular straw(Starving for Air, if it is adjusted for a Lower Alt, or Getting too Much Air if adjusted for a Higher Alt, and used in a Lower Alt)......

[joesgarage71]

Your hesitation is most likely the accelerator pump. have it rebuilt.

[VileZambonie]

Time for a rebuild