Author Topic: Which Carb Question  (Read 143 times)

Offline Kilian

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Which Carb Question
« on: November 18, 2019, 05:43:32 AM »
Hello all, first time posting here so be easy on me. I've got an 83 GMC C2500 (3/4 ton) that finally needs some attention. I'm trying to figure out the best Quadrajet to use on the engine. I've had it for about 20 years, getting it from a teen who was trying to rod it up a little (hence the Edelbrock intake and current rusty exhaust headers).

Here are the specifics:

350 engine (not original, CMJ suffix and engine VIN denote possible 1975 vintage)
Edelbrock intake
Moving to stock exhaust manifolds with dual exhaust
TH400 transmission
3.73 Rear Differential

Currently there is a 17085213 0576 HPB Q-Jet on the truck.
I also have three other Q-Jets I could use, 17082226 1482 DUU, 17081226 0231 DDS, 17080244 1640 CJL.

The current Q-Jet doesn't appear to match up with the Edelbrock intake directly (hopefully the picture posts correctly) but the carb sits inside of the round bosses on the manifold, if that makes sense. Maybe that's normal for an aftermarket intake.

Assuming that all four Q-Jets are stock and haven't been messed with internally, which is the best for this application?

The GMC is my farm truck that does some trailer pulling but doesn't see a lot of miles each year. Right now it burns very rich at idle, won't hold idle very well when hot, and I'm getting less than 5 mpg. I plan on doing the exhaust change this winter and thought I'd improve the carb performance at the same time if possible. Thanks for any help.
« Last Edit: November 18, 2019, 05:55:23 AM by Kilian »

Offline Cliff Ruggles

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Re: Which Carb Question
« Reply #1 on: November 24, 2019, 03:56:01 AM »
5 MPG indicates something is WAY off the mark someplace.

I'd start with basics, checking the timing, mechanical advance, vacuum advance and going thru the carb and putting one of our kits in it. 

Then evaluate performance and fuel economy and I'll bet you'll be remarkably surprised at how much better the engine runs everyplace......Cliff