Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

rochester carboretor specs

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by crithke, Jul 24, 2002.

  1. crithke

    crithke Registered Member

    Joined:
    Jul 13, 2002
    Posts:
    33
    Likes Received:
    0
    Location:
    Fairview, North Carolina
    i'm looking for specs on the factory settings for my rochester carboretor. if anybody could help it would be very appreciated...
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    I think you can find them in a Haynes manual, pretty sure they would be in a GM service manual, and more than likely in a "rebuild" kit.

    Problem is, specs changed every year, and some stuff won't be covered at all in any of those manuals, like primary rods/jets, and secondary rods/hangars.
     
  3. Goober

    Goober 1/2 ton status

    Joined:
    Apr 26, 2002
    Posts:
    2,222
    Likes Received:
    0
    Location:
    Mayberry (Auburn, WA)
    First of all, you need to find the number and date code stamped vertically on the drivers side of the carb. This will give you the correct application for the carb which is necessary when you go buy a rebuild kit. MOST rebuild kits will have documentation inside that gives you all of the specs that you need to reassemble your carb.

    One thing that you CANNOT get from the carb number is the jet and metering rod sizes. These will vary from casting to casting. For example; I currently have 3 quadrajets with matching numbers (except date codes) and they all have different size primary AND secondary rods. Even the secondary hangers are different. This is actually a good thing because it only added to my collection of available parts.

    If you post the numbers found on the carb then I'm sure someone would give you the proper specs for it.

    If you just picked up the carb from the boneyard and want to figure out what it came from then here is how you can figure that out:

    The following information was copied from dyeager535's web site

    Lets use this number as an example:
    7045213 YA
    101 5

    70 = Rochester products division#
    45 = Production year, 4=1970's, 5=specific year, 1975
    2 = Carb ID, 2=49 state Q-jet
    1 = Division, 1=Chevrolet products
    3 = Tranny ID*, Even number=Automatic, Odd number=manual
    101 5 = Julian Date Code, Friday April 11 1975
    YA = Engine assembly plant

    # Carbs starting with 70xxxxx are from 1975 and earlier. Carbs starting with 170xxxxx are 1976 onwards.
    Important note: Primary metering rods are different lengths for the two different series. Rods whose p/n starts with a 7xyz are for the 70xxxxx carbs, and p/n 17xyz are for the 170xxxxx carbs.

    * tranny ID is not cast in stone. This particular example was original equipment on an automatic equipped pickup truck.

    Production Year
    15 = 1960
    19 = 1961
    20 = 1962
    2x = 1963-1969
    3x = 1966-1967 A.I.R. equipped vehicles
    4x = 1970-1975
    5x = 1976-1979
    8x = 1980-?

    x=last digit of model year

    Carb ID
    0 = 49 state mono-jet
    1 = 49 state 2bbl
    2 = 49 state Q-jet
    3 = California mono-jet
    4 = California 2bbl
    5 = California and high altitude Q-jet

    Product Division
    0,1,2 = Chevrolet
    3 = Cadilllac
    4 = Buick
    5 = Oldsmobile
    6,7 = Pontiac
    8 = Non-GM, possibly Mercruiser Marine
    9 = Special

    Julian Date Code
    From our above example code;
    101 = Day of the year (1 thru 364/5)
    5 = Last digit of manufacturing year. (0 thru 9). Utilize carb id for 60's, 70's, or 80's.

    Engine Assembly Plant
    YA = ?
    FJY =?

    Examples:
    Our example carb number, 7045213
    Is a Rochester carb, for the 1975 model year, 49 state (federal) Q-jet, Chevrolet Division with supposedly a manual transmission.
    What it was originally installed on was a non-emmisions controlled 1975 3/4 ton Chevrolet Pickup truck with a 350 cubic inch engine and an AUTOMATIC transmission.

    How about another? 17083222
    Date Code 0183
    Is a 1983 model year, 49 state Q-jet, Chevrolet division with an automatic tranny.
    Manufactured on the 18th day of the year, in a year ending in 3. For, January 18 1983
    Originally installed on a 1983 1/2 ton Chevy Pickup with a 305 and automatic tranny.

    And one more for fun, 7043114
    A 1973, 49 state 2bbl , Chevrolet division, with an automatic tranny.
    Originally installed on a 1973 Nova w/350 and automatic tranny.
     
  4. crithke

    crithke Registered Member

    Joined:
    Jul 13, 2002
    Posts:
    33
    Likes Received:
    0
    Location:
    Fairview, North Carolina
    thanks for the help guys.. i don't think i need a rebuild kit as it was just installed about 2 years ago by the previous owner.

    my last question was fairly vague i now realize...i'm looking for the fuel/mixture settings of it...it would be a quadrajet installed on a 77 k5

    thanks
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    Only mix settings are the idle mix screws, if idle isn't bad, don't mess with them.

    Primary rods/jets, (and power piston spring) secondary rods/hangars are all "hard parts" with no adjustment. Only thing you can do is swap them with different ones, and the carb has to come apart for the primary side.
     
  6. crithke

    crithke Registered Member

    Joined:
    Jul 13, 2002
    Posts:
    33
    Likes Received:
    0
    Location:
    Fairview, North Carolina
    my idle is bad, it's terrible....it can't keep it's idle in park (just dies) sometimes. Also, it has a bad habit of idling at around 1500-1700 rpms...which most of you know is bad. I get a dieseling sound when i turn it off in park,which we all know is bad as well....that's why i'm looking for the factory settings on the carb in an attempt to make the mixture like it should be....anybody?
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    The carb "mix" setting thats probably wrong is the choke.

    Idle mix could be a problem alright, especially if the choke never opens fully.

    If idle was set high when you got the truck, I *guarantee* something else is wrong, because that is an easy way to cover up problems like vacuum leaks, bad plugs, wires, etc.

    Check that your choke is opening fully before doing anything else, and don't bend any linkage, or mess with idle mix screws, until you get it resolved. There is no "one size fits all" mix screw settings, I believe the factory method involves a vacuum gauge. Either way, it takes a little while to get idle mix wrong, IF it is the problem.
     

Share This Page