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Thread: 305 running like crap

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  1. #1
    Jagwar is offline Registered User Visit my Photo Gallery
    Join Date
    Jan 2005
    Car Year, Make, Model: 88 Jag XJS

    Question 305 running like crap


    I bought a Jaguar xjs with a chevy 305 engine, the previous owner put in a light cam, and it ran good but idled very rough. He sent me a rebuilt Roch Quadrajet, I put it in, made sure I have no vacuum leaks, and the car runs like crap. It will idle ok in neutral (1200rpm), but when I put it in gear (automatic), it drops to about 400 and is rough. Driving is worse, it surges without a throttle change, like its running out of fuel. I have screwed w the timing but am ready to put the old carb back on. Does this sound like a carb problem, float or something? I put an inline fuel filter ahead of the carb, and I can see the fuel in it.

    Also, the timing cover does not have the timing indicator on it, what is the best way to optimize the timing without a light?

    Are these rebuilt carbs normally tested and just bolt on and go?



  2. #2
    drg84's Avatar
    drg84 is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2003
    Car Year, Make, Model: 1996 Aurora Autobahn edition

    This is going to sound like i'm insulting your intellegence, but by any chance did you look to see if the Q-jet had a fuel filter in the canister? If so, it may be dirty/clogged. If thats not the case, here is what i would do. Set the car back to base timing. then get ahold of a Q-jet book or a chiltons/haynes manual. Both have the specs for Q-jet cars. set everything back to stock setting for your motor. You'll probably find it running a hair lean at this point. Richen it if needed. Finally, put a vacuum guage on the car and set the timing to optimal vacum off from a port below the throttle plates. Drive and enjoy
    Right engine, Wrong Wheels

  3. #3
    thesals's Avatar
    thesals is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2004
    san diego
    Car Year, Make, Model: 66 mustangFB, 69 econline Drag Van

    since you asked how to set your timing with no indicator, get cylinder 1 to top dead center, that means that the piston is coming up to compress fuel, both intake and exhaust valves will be closed.... then check and see which plug your rotor is pointing to fire, with the coil hot turn your distributo, with the cap on, until it sparks your plug for #1, that will get you to base timing...
    Last edited by thesals; 01-31-2005 at 09:44 AM.

  4. #4
    cbreezer is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2004

    I had a problem somewhat similar to that years ago.It turned out to be the timing chain/gear.

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