# Quadrajet problems



## jigaway (Jul 2, 2011)

Try to make a long story short here. Last week, I couldn't get my GTO started. Turned over but wouldn't catch. Had a carb guy come out. He took the newly purchased/rebuilt carb apart and it was flooded full of gas inside. He rebuilt it again. Finally got er fired up again. Took it for a 2-3 mile run and as I turned on to my home street, the car died. Couldn't get it started. Opened the hood and took the air cleaner off. The front butterfly was black on the passenger side, the top of the air cleaner filter was melted on the passenger side, the plastic piece that comes in to the cleaner from the breather was melted.

What the heck happened? 

I am thinking it is just a jinxed carb. I know the guy who rebuilt it said it was warped. Any thoughts?

Looking for a reputable place for a quality rebuilt Quadrajet?


Thanks in advance,

Dan


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## lars (Sep 28, 2004)

There aren't too many "carb problems" that will cause the symptoms you describe. Sounds more like you have a couple of cam lobes going flat. Pull your valve covers off and see if all your valves are moving the same amount when you crank the engine over - I'll bet you have some exhaust valves not opening fully due to flat lobes.

If you still suspect the carb, send it out and I'll go through it and test run it on the run engine, but I have a funny feeling the carb is going to check out fine...

Lars


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## BearGFR (Aug 25, 2008)

Do you know how much fuel pressure is being supplied to the carb? Your symptoms are making me suspicious that it's flooding either due to excessive fuel pressure or a non-functional needle/seat/float assembly. If the guy didn't test the float when he rebuilt it, he could have set the float level perfectly and the carb still be hemorrhaging fuel if the float doesn't float... 

The black and the melting sounds like it's been on fire under there, which definitely can happen if the carb is puking fuel. I sure wouldn't try to drive it until I got it all sorted out - you could lose the whole car.

Bear


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## jigaway (Jul 2, 2011)

@Lars- It has <2k miles on a new Cam. Rebuilt engine. Doesn't mean what you are suggesting isn't true. I'll check it out. Appreciate the idea.

@bear- I don't know how much pressure it is getting. Is a brand new fuel pump. My enging builder, not seeing the car, thought the same about hemorrhaging and burping fuel. He thought something isn't right about the carb since it is warped.

The car was running flawlessly until I let it sit a few weeks during bad weather. 

I talked to my enging builder and he said the same thing several others have.. Buy a brand new Edelbrock. I must admit there is something appealing to me to get something new locally, instead of chasing Qjets over the internet.

Dan


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## BearGFR (Aug 25, 2008)

I understand the desire to just make the problem go away so you can enjoy the car. 

Since it was ok until it sat for awhile, you might consider going through the carb yourself. Grab a copy of Cliff Ruggles's book on the subject (you can also get quality rebuild parts from him on his web site), and just take your time and work through it. A large percentage of the time, the main problems with QJet's come from "the last guy that worked on it" and thought he knew a whole bunch of "secret tricks", and really just messed it up.

lars has some good articles "out there" about working on them too.

Look at it this way: it's already not right, so there's no reason to be afraid of tearing into it. At the very least, you'll learn something.

Bear


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## chuckha62 (Apr 5, 2010)

You say you have a brand new fuel pump. That makes me suspicious right off the bat. Is it an AC Delco? If not, you MAY have ID'd your problem. Most aftermarket pumps simply put out too much pressure for a Q-jet.

Been there, done that!

Chuck


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## lars (Sep 28, 2004)

Stock mechanical pumps put out between 4 - 6 psi, and a Q-Jet can easily handle 7 psi.

There are no carb problems that will cause the plastic parts inside the air cleaner to melt down. If the carb is showing sooting on the one side, and the temperature has gone high enough to melt the filter element and the PCV breather components, you have exhaust valves on the one side of the engine which are not opening - flattened cam lobes. Flattened exhaust cam lobes will cause the hot exhaust gasses to be pushed up the intake manifold and will make the air cleaner so hot it cannot be touched, melting the plastic parts. 2,000 miles on a new cam is about the right amount of time for the lobes to go flat - I really suggest you check it out - it takes about 5 minutes to verify.

Also, a warped carb airhorn will not cause the carb to flood. If the warpage is severe, it will cause the engine to not idle due to interupted fuel continuity between the bowl and the airhorn, but the carb still won't flood - the needle/set will still close off no matter how warped the airhorn is. Again - if you want me to check the carb out for you on my run engine I'll be glad to give it a checkout and a test run for you, but you better check those exhaust valves first...


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## jigaway (Jul 2, 2011)

@Lars- I'll talk to my engine man about checking for checking on flattened lobes.

Meanwhile, is there a tutorial or written instruction for this procedure??

thanks,

Dan


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## lars (Sep 28, 2004)

Pull the valve covers off. Disconnect the coil "+" wire. Have someone crank the engine over while you observe the movement of the rocker arms: All rockers should move about the same amount. If you see one or two that are not moving as much as the others, you have a flat cam. Pull the intake and the valley pan off the engine and remove the damaged lifters: The lifters will be caved in on the bottom and the cam lobe will be ground flat. This can happen with no lifter clatter or noise, and it will cause the air cleaner to get up to several hundred degrees hot.

I've seen this happen on about a dozen engines, so it's a very common issue.

Lars


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## jigaway (Jul 2, 2011)

Thanks for the info. Talked to my engine man. We'll test it out. Really appreciate your thoughts.

I'll let you know what we find out.

Thanks again,

Dan


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## lars (Sep 28, 2004)

Good luck - I hope I'm wrong...shaved cam lobes make one heckuva' mess out of an engine...
Lars


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## jigaway (Jul 2, 2011)

Was just inspecting my car under the hood. Looks like oil shot up through the breather tube and in to the air cleaner. I found a thin coat of oil on the breather tube side of the air cleaner pan wher the filter was melted.. I have a feeling this is gonna hurt. 
@ Lars, I think you were right. Carb is probably ok, Gonna have my engine guy over this week to inspect er.

Dan


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