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Old 07-15-2010, 01:00 AM
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Is my Q-Jet Toast?

Looks like the throttle shaft journal for the primaries has a pretty good sized crack in it on the linkage side. Any saving it or is it time to get a new carb?

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Old 07-15-2010, 01:21 AM
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When I was using a Q Jet I rebushed my throttle shafts with a kit from Jet.
Bushings, drill bit and reamer included.
Jones Performance Fuel Systems, (714) 848 5505, if the info is still good.

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Old 07-15-2010, 04:16 AM
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Quote:
Originally Posted by clicketyclack
Looks like the throttle shaft journal for the primaries has a pretty good sized crack in it on the linkage side. Any saving it or is it time to get a new carb?
You might be able to locate a throttle plate to replace yours with. Do you have the carb number handy?
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Old 07-15-2010, 09:32 AM
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there has to be 10 million Q-jets out there, check eBay or the scrape-yards. Try to match your numbers as close as you can and use both carbs to make a good one. There were only 2 sizes, primary venturi is completely round on the small size, has a lump on the large size.
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Old 07-15-2010, 09:41 AM
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A bit of trivia that doesn't seem to be widely known, is the 800 CFM Q-jet was used almost exclusively on the later trucks, right up until they went to feedback.

As hard as it might seem to believe, even the non-feedback Q-jet that came stock on a '86 Sierra 4.3L V6 was a 800!
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Old 07-15-2010, 11:17 PM
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That should make mine an 800 then, It was original to the truck, a 75 C20.

Thanks for the suggestions. I was able to go to the scrap yard (unfortunately the closest one that deals with much for old Chevys is a little over an hour away) and I found a nearly identical casting number. Matches as a 1975 Chevy quadrajet, except this one was for an MT while mine is an AT. I was able to adapt the throttle linkage by removing the extra bracket and adding the throttle attachment from the old one where it was supposed to be. I had to hold the round end in a vise while I turned the nut, but it went on OK.
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Old 07-16-2010, 10:21 AM
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Quote:
Originally Posted by clicketyclack
That should make mine an 800 then, It was original to the truck, a 75 C20.

Thanks for the suggestions. I was able to go to the scrap yard (unfortunately the closest one that deals with much for old Chevys is a little over an hour away) and I found a nearly identical casting number. Matches as a 1975 Chevy quadrajet, except this one was for an MT while mine is an AT. I was able to adapt the throttle linkage by removing the extra bracket and adding the throttle attachment from the old one where it was supposed to be. I had to hold the round end in a vise while I turned the nut, but it went on OK.
You are right on the cusp for having the best chance of your Q-jet being a 800 CFM unit. 1976-up is usually the recognised division- but the only way to know for sure is to look at the primary venturi to see what it is.

Truth be told, I'd just as soon have the smaller venturi carb for most applications, anyway. It's not like many SBC's need more than 750 CFM.

Good luck!
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