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Thread: Date coding explained

  1. #1
    Certifiable ozbox's Avatar
    Join Date
    Mar 2010

    Date coding explained

    most people would not have any idea how to date code a motor or a part that has the coding on it but would have heard about it..its very easy..
    to start i will only explain australian date coding as anyone interested in a sandman, these vehicles will have this system..
    what you will see is a number or numbers and a letter and then another number...lets say 28D5..sometimes a d on a motor as a rough casting may look like an O..there is no o in date coding.
    I=NOTHING as it can be confused with the number they skipped I :Chin:
    the numbers will correspond with the amount of days in that particular month.
    so we have numbers first then the letter and the number at the end is.....
    the 28D5 is the 28th day of april 1975....

    i shall explain later about american date coding....why you ask...:errf:
    because gmh used american date coding on its australian motors till llate 1972 somewhere..i just need to verify a date if its known...

  2. #2
    Certifiable ozbox's Avatar
    Join Date
    Mar 2010
    the american style date coding can be confusing if you have been taught the oz way but we shall try and explain as simply as possible...we shall use with permission from scott at concourse parts a couple of pics from his blogspot..we shall use his november 1972 hq ss as a guide...the yankee way worked on month first..then day date..then L242 is november 24th 1972..this system seems to be used on the cast parts like engine exhaust manifolds diff centre section etc and was used from the beginning of holdens engine production till at least december 1972 that we can find jones if he pops in may be able to give us an exact basically it is the same principal but the australians simplified it..

    for more date code type pics in oz and yank versions go here to scotts blogspot

    something interesting about the date coding on the early hq is that there is a combination throughout scotts ss that is both types.
    Last edited by Alien DNA; 01-06-2018 at 12:31 PM. Reason: more stuff added

  3. #3
    Super Moderator Absinth's Avatar
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    Feb 2010
    Junee, NSW

    Rochester carb dating

    70 - Prefix for Rochester carburetors

    Decade Identifier

    2 - 1960's
    3 - 1960's
    4 - 1970 to 1975
    5 - 1976 to 1982

    Year of Manufacture
    7041240 Not the model year

    6..........1966 or 1976 with a leading 1 in code
    7..........1967 or 1977 with a leading 1 in code
    8..........1968 or 1978 with a leading 1 in code
    9..........1969 or 1979 with a leading 1 in code
    0..........1970 or 1980 with a leading 1 in code
    1..........1971 or 1981 with a leading 1 in code
    2..........1972 or 1982 with a leading 1 in code
    3..........1973 or 1983 with a leading 1 in code
    4..........1974 or 1984 with a leading 1 in code
    5..........1975 or 1985 with a leading 1 in code

    After 1975 Carb will have an 8 digit code starting with 1 - i.e; 1704..

    Model Federal / California 7041240

    0 - Mono-jet........1-bbl........Federal Standards
    1 - Two-jets........2-bbl........Federal Standards
    2 - Quadrajet.....4-bbl........Federal Standards
    3 - Mono-jet........1-bbl........California Standards
    4 - Two-jets........2-bbl........California Standards
    5 - Quadrajet.......4-bbl........California Standards
    6 - Varijet............2-bbl.........Federal Standards


    0, 1, 2, Chevrolet
    3, Cadillac
    4, Buick
    5, Oldsmobile
    6, 7Pontiac

    Transmission 7041240

    1,3,5,7,9 - Odd numbers - manual transmission
    0,2,4,6,8 - Even numbers - automatic transmission

    Carburetors produced until 1969 begin with a 702 followed by four additional numbers.
    The 5th number is either a "1" or "2," indicating federal (49 state) emissions, or a "4" or "5" denoting California emissions.
    The 6th number indicates the division application. "8" is Checker and Marine. The last number indicates the exact application. For the most part, even numbers were used on automatic transmissions, and odd numbers on manual transmissions, but there were numerous exceptions.

    For carburetors produced from 1970 to 1974, the first three numbers are "704" followed by the same sequence of numbers as the "702" series of carburetors. (Some 704 carburetors were produced early in the 1975 model run; later units start with "1705.")

    1975 and later Carbs
    Staring in the 1975 model year, a "1" was placed in front of the "7" followed by "705." The "1705" series of carburetors would run until 1979. Beginning in 1980, the first four numbers were changed to "1708," and this number series would continue until the last carburetors were produced in the late 1980s.

    Most Rochester built Q-jets used a four-number Julian date. The first three numbers are the day of the year the carburetor was built; the last number is the year.
    For example:
    Carburetor number 17058201 followed by a Julian date of 1238 would have been built the 123rd day of 1978.
    One must keep in mind when dating carburetors that the year of production may not always be the same year as indicated by the carburetor number. Quite a few service replacement carburetors were produced. It is quite common to find much later production dates then what is indicated by the carburetor number.

    Information from,
    "Rochester carbs by cliff ruggles"
    Last edited by Absinth; 10-07-2010 at 12:49 AM.
    4/75 HJ XX7 Sandman Panelvan ... Persian Sand currently restoring
    7/76 HX Monaro 4dr 308 4sp... Absinth Yellow and rusty as hell.. SOLD
    3/77 HX Sandman Panelvan ... Absinth Yellow and rusty as hell .. SOLD

  4. #4
    Certifiable ozbox's Avatar
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    Mar 2010
    nice add on sean...:D :D

  5. #5
    Forum Mum jennie285's Avatar
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    Apr 2010
    Parkes Central West NSW

    our 253 rebuild

    Our van was built during the 10th month 1977, and the engine number on the block is
    19G7 which from reading the codes above should be 19 july 1977 assuming we have read all the info correctly this motor should be near enough, as was built 2-3months previously to being correct. if anyone has any opinions please advise...

    Engine number is QR887183
    Last edited by jennie285; 23-10-2010 at 07:09 PM. Reason: added engine number

  6. #6
    Sandman Guru
    Join Date
    Jul 2010
    Also be careful of some SBC stuff as they used I in the early days!

  7. #7
    Sandman Driver mook's Avatar
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    May 2010
    Interesting.. i had a look at my engine at the date cast

    Looks like JJ(or a 7)51 with the little clock pointing closely to 6.

    The start of the engine no is 11QT


    Any ideas?

    Trimatic pattern as well..
    Last edited by mook; 24-10-2010 at 03:37 PM.

  8. #8
    Certifiable ozbox's Avatar
    Join Date
    Mar 2010
    dunno about your cast date but the engine number prefix is for hq thru to mid hz statesman..

  9. #9
    Night Rider Blocker's Avatar
    Join Date
    Feb 2010
    Behind the keyboard.
    Engine date code will be found as marked;

  10. #10
    Cruiser razsandman's Avatar
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    Jul 2010
    the 4 253 i have here are : 12J3, 18J8, 16G2, 31A9. I think i still have one or maybe two in the back of my dads shed.

    how does the coding and numbering system work. how do you match one to your cars manuf date??
    1976 HJ XX7 Sandman
    Genuine VN SS manual atlas grey
    HX LE Coupe project

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