Quadrajet Head scratcher
Thread Starter
Intermediate
Joined: Apr 2009
Posts: 36
Likes: 2
From: las vegas
Quadrajet Head scratcher
Hi all, I have a 1978 L82. Has the Quadra jet carburetor on it and was running great. Started it the other day and it was flooding the bowl with gas and I was barely able to keep it running. Then after 2 or 3 minutes it did a 180 and the bowl went empty and it died. It will start but runs out of gas in the bowl. Seems like something is keeping it from getting gas into the bowl. I replaced the fuel pump and that made no change. I took the air horn off and pulled the float and needle out and everything looks fine. Fuel filter is clean also. Before all this it was running perfectly. A real head scratcher. Do these q-jets just go bad. Could it be the high engine bay temps warped the carb? My temp gauge stays around 190 but it gets super hot in the engine bay. So hot that it melts the rubber on the passenger side air cleaner boot. Any help would be greatly appreciated. I just can't figure it out.
Corvette Enthusiast
Joined: Oct 2007
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From: So. Cal.
2025 C7 of the Year Finalist- Unmodified
2024 C7 of the Year Finalist - Unmodified
2023 C7 of the Year Finalist - Unmodified
I have always preferred Holley carbs over Q-jets. Holley carbs are so simple to work on. And replacement parts are available.
Le Mans Master
Joined: Aug 2005
Posts: 6,529
Likes: 1,964
From: Temple Terrace Florida
When set up correctly, the Q-jet is a great carb. GM used them on millions and millions of cars in many configurations. Depending upon when it was last serviced, consider having it professionally rebuilt. Lars comes to mind. Jerry
Le Mans Master
Joined: Apr 2001
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From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
You might want to check the pump pressure, I hear some of these new pumps are too high and that could cause the flooding issue. Not sure about it going dry shortly after though. Maybe Lars will step in with some of his Qjet advice.
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
Replace the needle and seat with one from either cliffs or napa. Maybe have lars go through it. But with quality repair parts not on every corner you might consider a Holley. They make a decent q jet replacement carb
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
You need to test and verify what your fuel pressure is at the carb inlet and proceed with troubleshooting based on those results. No, a carb does not just "go bad," and engine temps won't warp a carb unless you have en engine compartment fire. Your carb is one of the high performance 800 cfm carbs, and there is no carb better suited to your engine - the recommendations above that you replace it are not good recommendations. You need to do proper troubleshooting and repair - not just random parts replacement.
Lars
Lars
Last edited by lars; Jun 24, 2022 at 12:04 PM.
Thread Starter
Intermediate
Joined: Apr 2009
Posts: 36
Likes: 2
From: las vegas
Thanks to all for the advice and comments. I checked the fuel pressure at the carb and it was 6 psi. Still baffles me why it starves the bowl. I'm not a great carburetor fixer so I went ahead and rebuilt a Holley 6210 and stuck it on there and it fired right up. I know the q-jets are awesome when set up right, I just don't think I can keep it up and going. Lars, thank you for the expert insight. I'll go through the q-jet and if anything learn from it for the future. For now I'll see how the Holley holds up. Thanks again to everyone. Awesome site.
