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Old 10-24-2012, 09:46 PM
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As you probably know, there are other things that affect how a carb will work on a particular engine besides the easy-to-change jets and metering rods.

The idle circuit is what mainly needs work, but in your case- having a relatively small displacement engine- this will not be a bother. In fact the idle and transition calibrations used in the later years before EFI (that were often too lean) will actually work good on your engine.

The carb numbers I'm giving you here are for NON computerized/ NON feedback carbs. These were used on light trucks and vans for years after passenger cars all had gone to feedback carbs requiring a computer to run right.

One application that will work good w/o needing a lot of work is a 4.3L Chevy/GMC Q-jet from 1985-86. Here are some specs:

Carb number 17086047 1986 4.3L V6 Sierra w/MT
74 primary jets x 55A primary rods
EH secondary metering rods on a “J” hangar

17086046 is same carb internally, only real difference is it has a throttle arm that will allow a TC cable to be attached. I don't know what trans you have so I don't know if you need that throttle arm or not. The difference between an AT and manual throttle arms is the AT arm is extended below the throttle shaft. This allows a cable to be pulled by the arm. But the idle and transition circuits will be good (or very close) as-is, the main changes you may need to make will be primary and secondary metering rods and primary jets along w/the power piston spring. You will adjust the secondary spring and vacuum pull off as needed.

Similar carb to Sierra, w/AT- 1985 Chevrolet Truck 350 V8 17085213; 17085003 (V8); 17084226 (rear po)
(17088040, 17088041?)
(17086045, 17086047, 17086053, 17086055?)

The following carbs have a dual capacity accelerator pump: 17086046, 17086048, 17085227 (AT); 17086054 (AT), 17085210.

These numbers: 17084502 (MT) and 17085211 (fits 1985-86 MT truck) may work too, I'd need to double check them.

As far as using an original Q-jet for a Sprint engine, they're rather rare and could be expensive. Not to mention they're old and would likely need to have primary throttle shaft bushings installed, plus there's always the chance the castings could be warped, etc.

The newer 1976-up carbs w/the late-type casting are going to be more plentiful and should generally be in better condition. They have improvements over the older carbs like an improved float arrangement and an electric choke. They're also well understood like the older Q-jets and parts and info are readily available.

Some info and links on tuning here.

Cliff Ruggles has a good Q-jetsite and also has a book out that's full of info. Other links, etc. here.
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