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Rochester Carb m4mE

Discussion in 'Chevy Trucks' started by Razzlo, Jun 22, 2001.

  1. Razzlo

    Razzlo Member
    Messages: 33

    C10/350 w/ Roch. M4ME and i have a couple of questions.
    1). Engine Running very rich. Can I adjust the mixture with the APT screw in the front of the carb. or do I need to get to the individual mixture screws and if so:
    2). Where are the screws and how can I get to them?
    3). on the back if the carb there seems to be a bolt coming out, but I cannot find this on any diagram. Anyone have any ideas?
    This carb does not have a solenoid or ECM module.
  2. MTCK

    MTCK Senior Member
    Messages: 346

    I believe these carbs come with the mixture factory set, and a plate in front of the screw so that you can't adjust them, if I recall how my quadrajet was. What you have to do is drill out the plate to reach the mixture screw. Or just re-jet it.
  3. Razzlo

    Razzlo Member
    Messages: 33

    It looks like there are a couple of adjustment 'knobs' i'll call them on the front of the carb, below the body. I cannot get a socket to fit them. I cannot tell what size they are. What are these for? Thanks.
  4. Fixxer

    Fixxer Junior Member
    Messages: 1

  5. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    I have this carb on a Dodge, so there might be some differences.
    The knobs coulld be limiting caps so you cant turn the mixture screws. Thats where they are though, in front in bottom section, one each side next to vacuum ports. Takes a tool to adjust them. The screw head looks like (__) if you were to draw a line across the top of that. the screw would be male and the tool which might come on a flex cable with handle,w/ female end like a socket. Check the tool section at a good auto parts store. There vacuun ports on the back of the carb, one large for canisters, one small. Don't think theres a bolt other than the hold down bolt.
    If the mix screws are sealed, look for other reasons it's running rich. Maybe a vacuum line came off from choke pull off or back of the carb, damaged nozzle in carb throat(I did this once).
  6. festerw

    festerw Senior Member
    Messages: 986

    We spent all last summer screwing around with the Q-Jet on our boat, we finally gave up and are running a Holley Pro-jection TBI system now.
  7. Dan S.

    Dan S. Member
    Messages: 31

    Those adj screws only adjust the idle mixture circuts, check to see if your choke flap is opening, check the bi-metal spring in the intake manifold that sets the choke, there is a vacum operated choke pull off on those carbs also, could also be a float level problem or debris in the float valve, do you have a fuel filter on it?
    The bolt in the back ? could someone have plugged a vacum port with the bolt? Vacum leaks cause a lean condition.
    Good luck
  8. Tommy10plows

    Tommy10plows Senior Member
    Messages: 345

    The Rochester Quadra-Jet is quite possibly the greatest carb ever built. When properly set up it will run smoother, idle better and pollute less than any other carb on the market.

    The problem is, there are darn few good carb shops around any more, even though parts are still widely available. Set up involves the right metering rods for idle mix, the right idle mix screw adustment, correct jet size for intended use, float level settings, adequate air flow through the correct size air horn and filter, and of course good clean gasoline.

    I run Rochester quads on my Chevy powered boat,and those engines are the sweetest running, smoothest idling, easy to care for products ever to set their feet in the water. Plus, when you kick in that secondary link, you get a smooth and reliable run up to the max RPM of the engines, in my case at 4400 RPM.

    Only wish that the Carter YF on my 4 banger Jeeps would kick in like the quadrajets do!!
  9. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    If you want to "do it yourself" I recommend this book.......
    HP Books- Rochester Carburetors, by Doug Roe
    ISBN: 0-89586-301-4