# Dramatic loss of power



## BigDuke0767 (Mar 1, 2011)

Reciently I installed a quadrajet carb that was remanufactured. I got the timing dialed in and the car runs great at idle. Put it in gear and drive it is another story. If I just take off at the light like an old lady and keep it above half throttle it will run fine. But once I attempt to go any further past that it falls completely on its face. It has even stalled out on me once. if I can feather it out and work threw that rough part it will run great at WOT. But getting past that is the hard part. Any ideas what might be causing this?


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## rickm (Feb 8, 2012)

has this condition existed from the initial start up with the remaned carb? it might have got bounced around during shipment. new fuel filter? accelerator pump working? does a flooding condition exist ?


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## geeteeohguy (Feb 2, 2008)

Sounds to me like severe fuel starvation during the transition from idle to cruise. I would check the accelerator pump circuit. If not shooting two strong streams of fuel, return the carb under warranty for another one. Good WOT performance tells me that the float, main metering, secondaries, fuel pump, etc, are all ok. Question: why did you install a reman carb in the first place? Did you have this same problem before the install??


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## BigDuke0767 (Mar 1, 2011)

When we got the car it came with an edelbrock intake and a Holley 4bbl. I found in my stash of parts that I had an original intake for it and I got the reman carb for Christmas 2 years ago. The Holley was too temperamental and since I want to put the car back to a more original condition I switched back. The reman carb came from summit so I might have to give them a call. Could it be possible that I'm getting too much fuel since I don't have a pressure regulator?


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## BigDuke0767 (Mar 1, 2011)

Also in my stash of parts I found a Pontiac correct 1968 q-jet I'm thinking about rebuilding. I think I'm going to that it to Cliffs high performance and see if he can do anything with it.


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## chuckha62 (Apr 5, 2010)

You may want to see what you have for a fuel pump. Holley's tend to be more tolerant of higher pressure than Quadrajets are. As I understand it, the original AC Delco pump was calibrated to produce less than 5 psi of pressure. Aftermarket replacement pumps typically are in the range of 7+ psi. This is usually too much for a q-jet and can unseat the needle and seat in the float bowl. Typically, it will run too rich at idle though and your air screws will have no real affect. 

Just something to consider...

Chuck


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## jetstang (Nov 5, 2008)

pull the carb and stick a new baseplate gasket on. Also make sure all the vacuum ports are hooked up or plugged, sounds like a huge vacuum leak to me. May be a bad carb. Also, look for smoke after turning the car off and watch for smoke from the carb, that means it's dumping gas.


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## BearGFR (Aug 25, 2008)

Check the easy stuff first. Engine off, look down through the carb and work the throttle - verify you''re getting squirts of fuel from the accelerator pump. If not, that's probably the problem. Make sure the pump linkage is connected (see attached photo).
If all that's correct and the pump is moving, but you still aren't getting a shot of fuel, then the pump itself is bad and needs to be replaced.

Cliff's really good on QJets, but he's also severely backlogged on work (months). A basic rebuild is something you can do yourself easily though, just grab a copy of his book (How to Rebuild and Modify Rochester Quadrajet Carburetors) and work through it. You can get good parts from his web site, too.

Bear


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## BigDuke0767 (Mar 1, 2011)

I have a fuel pressure regulator that I'm going to try out. The weather just hasn't been cooperating with me. I'm going to try the easy stuff first. Does anybody have a diagram for the vacuum lines? Just to make sure i have them hooked up correctly. Also the car is a numbers matching 1967 GTO with the His&Hers hurts shifter in it.


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## lars (Sep 28, 2004)

The commercially "remanufactured" carbs, especially those from Holley and Summit, are a real bag of worms, and typically have a slew of problems that make them almost unusable in many cases. You can drop me a note for my "Commercially Rebuilt Q-Jet Problems" paper for a listing of the common issues and problems that I see during my "Tuning for Beer" seminar series: Cliff and I see the same problems and issues, and we both recommend that these carbs be avoided at all costs. If you'd like me to check the carb out on my test run stand to identify the problems, I can usually do a basic teardown, inspection, and test run diagnosis for about $35 plus return shipping - costs increase if a complete rebuild and parts are required. You can e-mail me for my "Services Info Sheet" for a full description and outline of the services I can do withthe carbs and distributors.

Here's a Pontiac 800 cfm Q-Jet being tested on a Pontiac engine. The test setup is instrumented for air/fuel ratio, vacuum, timing, and rpm - each carb is run through a complete test profile to assure fast idle, cold-start, hot idle, idle mixture, and secondary operation.









I also do a new Holley and BG setup service to assure that new carbs are set up right for the engine application: You'd be amazed how far out of adjustment a new carb is right out of the box. This new Holley Street Avenger had a half-dozen issues that needed to be corrected before it was deemed acceptable - this carb was run on my 357 Chevy small block run engine:












For information on the carb setup and rebuild services, just drop me an e-mail request:

Lars
[email protected]


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## geeteeohguy (Feb 2, 2008)

For $35 and shipping, that would be my first choice. Can't beat that deal for being thorough, IMO.


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## BigDuke0767 (Mar 1, 2011)

Well the weather has broke here in Ohio and I was able to try the pressure regulator. It actually made it worse. So i took the regulator off and am back to square 1. The accelerator pump is also working I tested that and it's got a good stream. It only does it when it's under a load so could it be a vacuum leak?


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