Quadra Jet
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2nd Gear
Joined: May 2024
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Quadra Jet
Recently purchased a reman Q-jet for my 84 El Camino, stock 305. Take off flange or base gasket had enclosed primaries and open secondary area. New gasket that came with the reman is entirely open and thicker. Idle circuit is fine now, but acceleration is poor and wants to surge with moderate acceleration. Any idea about what’s going on here? Thanks, Jerry….
Melting Slicks
Joined: Apr 2021
Posts: 2,549
Likes: 2,009
From: Minnesota
Yes, this is a corvette forum. If you have any additional questions about your car there are El Camino and G-Body forums that might be able to give you better information.
To answer your question though, it’s likely that your issues with your Quadrajet stem from the fact that it is a remanufactured carb likely using incorrect parts mixed and matched from different models and set up in a way that would never perform correctly on your 305. The user Lars on this forum has a lot of posts mentioning the pitfalls of these carbs.
You can find one here:
Photos of Some Problems with Commercially Rebuilt Q-Jet
To answer your question though, it’s likely that your issues with your Quadrajet stem from the fact that it is a remanufactured carb likely using incorrect parts mixed and matched from different models and set up in a way that would never perform correctly on your 305. The user Lars on this forum has a lot of posts mentioning the pitfalls of these carbs.
You can find one here:
Photos of Some Problems with Commercially Rebuilt Q-Jet
Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,328
From: At my Bar drinking and wrenching in Lafayette Colorado
Your problem is that you have purchased a "remanufactured" carb. I can tell you, without hesitation, that it is a complete POS that has been pieced togteher form various mismatched years and models of carbs, and you will not be able to get it running right regardless of the base gasket configuration. Find a good, used, unmolested carb for your year car and have it properly rebuilt by someone qualified to do so. Send me an e-mail if you would like a copy of my article about the problems I have seen with your "remanufactured" carb. It is junk, and you can't fix it without significant effort and expense (The General Manager of JEGS High Performance is currently sending me the reman carbs he has bought for his collector cars to get them repaired and running right - and they are junk...)
Lars
Lars
Drifting
Joined: Nov 2021
Posts: 1,701
Likes: 375
From: People's Republic of Nueva York
Recently purchased a reman Q-jet for my 84 El Camino, stock 305. Take off flange or base gasket had enclosed primaries and open secondary area. New gasket that came with the reman is entirely open and thicker. Idle circuit is fine now, but acceleration is poor and wants to surge with moderate acceleration. Any idea about what’s going on here? Thanks, Jerry….
Quadrajets aren't voodoo, but they're not interchangeable either, even though they all look the same.
If you still have your original, definitely send it to Lars. Make the investment and get your car running like GM intended.
Racer
Joined: Mar 2020
Posts: 384
Likes: 144
From: Langton, Ontario, Canada
2025 C4 of the Year Finalist - Unmodified
The surging is a sign of lean mixture. It sounds like the Q jet is adjusted for too big of an opening on the secondaries. It has potential to adjust up to about 850 CFM, and it's probably opening up too big for your 305 that only needs about 600 CFM. There is an adjustment under the lid at one end of the secondary air valve that you need to adjust to open not so much under full throttle. It's been a long time since I worked on QJets, but you should be able to find that adjustment on YouTube or by Googling it.
