Carb too lean?

Discussion in 'The Venerable Q-Jet' started by FireRedGS455, Dec 18, 2021.

  1. FireRedGS455

    FireRedGS455 Founders Club Member

    Thanks.
    The Carb is a Roch Qjet 7041540. I think there is a small sticker on the fuel inlet piece of the carb saying CJ, if that means anything.
    I will check plugs, but there is no sooting tailpipes and if I recall correctly no carbon build up on plugs. However I will check.
    My understanding is that the carb/engine is reacting perfect. No hesitation from standing start or when rolling and kickdown. Not even at normal cruise.
    It roast the tires imidiatly and the tires squeals when going from 1st to 2nd at WOT. I have a shift kit in the original, numbers matching THM400.
    I even match presumably quick cars (more hp) on the first part of the 1320ft, then my limited breathing capabilities (Stock intake and heads) is hurting.

    I don't no what the APT feature in the baseplate is? but to me the carb seams stock with the setup shown in the picture.
     
  2. FireRedGS455

    FireRedGS455 Founders Club Member

    I will check that.
    Thanks
     
  3. FireRedGS455

    FireRedGS455 Founders Club Member

    Thanks.
    I'm not sure, so I will check if it goes higher with RPM. I don't have much experience with this, but I'm learning.
    So the AC system is complete. All parts are there, it has worked fine, there is not any more refrigiant in the system so it does not work.
    The fins in the condenser is fine and nothing is blocking the airflow.
    I don't remember the size of the trans cooler, next time I'm at the car I will measure it. It is in winter storage at a friend.
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If you read my power timing thread, it will tell you the whole purpose of using the lightest springs you can find, to check and set your total timing (without vacuum advance), is so the weights swing out to their maximum at a relatively low RPM. That way, you can be sure there is no more mechanical advance left in the distributor. For some reason, guys read the thread, but they get it in their head that all you have to do is rev the engine to 2500 RPM, and set the timing they want there. If there is more advance left in the distributor, it will advance beyond that.
     
    69GS430/TKX and 72STAGE1 like this.
  5. BQUICK

    BQUICK Gold Level Contributor

    What water temp gauge and sender are you running? Maybe it's a liar.....
     
    FireRedGS455 likes this.
  6. Cliff R

    Cliff R Well-Known Member

    If you read my power timing thread, it will tell you the whole purpose of using the lightest springs you can find, to check and set your total timing (without vacuum advance), is so the weights swing out to their maximum at a relatively low RPM. That way, you can be sure there is no more mechanical advance left in the distributor. For some reason, guys read the thread, but they get it in their head that all you have to do is rev the engine to 2500 RPM, and set the timing they want there. If there is more advance left in the distributor, it will advance beyond that.

    +2

    I would also add here that a factory HEI has a design flaw built into it. They "slot" the advance pin rides in does NOT provide a "positive stop" for the advance. Instead it relies on the "flats" on the center cam and weights. When the advance reaches a point where the weights are even on the flats of the center cam the advance curve stops. Problem with all that is that using lighter springs can and will allow the weights to "roll out" past the flats and continue to add timing. This may not happen to well past 4500-5000rpms so you may not see this simply "power timing" it with a tach and timing light.

    Here I weld in a positive stop for all HEI builds, and double check the work with a degree wheel before installing the distributor in an engine or on a distributor machine. This way I already know exactly how much timing it will add and just need to see when it comes in..........Cliff



    IMG_1500.JPG Pontiac HEI (2).JPG
     
  7. Mart

    Mart Gold level member

    Cliff, any special brand of grease / lube that you use on the weight pads?
     
  8. Cliff R

    Cliff R Well-Known Member

    I use a high temperature Moly base grease that I buy at our local Tractor Supply Store.

    All of it will eventually dry up and get crusty, but that usually takes about 20 years or so. I just went back thru the HEI in my 455 after it spent over 30 years in service in three different engines. It started to stick just a tad and wouldn't pull all the way back below about 1000rpms or so. I rebuilt that distributor in the late 1980's and that's the first time I've had to touch it.........
     
    FireRedGS455 and Mart like this.
  9. tommieboy

    tommieboy Well-Known Member

    Sometimes radiator hoses look good but collapse as RPMs increase, even with a good radiator cap. Easy to check for, especially once the engine is up to operating temperature.

    Also, the fan clutch, if you are running one, can fail and cause cooling issues.

    I typically check the two items above before moving on to the carburetor, distributor, etc.

    Tommy
     
  10. 72STAGE1

    72STAGE1 Runnin' with the Devil


    How do you check the fan clutch?
     
  11. tommieboy

    tommieboy Well-Known Member

    Testing mechanical clutches can get pretty involved like anything else, but I typically do the following as my initial quick and dirty test. With the engine turned off and cold, if you try to spin the fan by hand and there is no or minimal resistance, then the fan clutch typically needs to be replaced. I am not heavy-handed but could never spin a fan with a good mechanical fan clutch more than a third of a rotation.

    Tommy
     

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