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GTO Engine Codes

Engine Identification
    1. Production Date Code
    2. Block casting number
    3. Engine Code

1. Production Date Code on the block. This can be found on the distributor pad. It consists of letters A-L for month (A=January, etc.) One exception is that 1966 blocks made for 1967 model year have an M for December instead of L. The second digit or digits (there could be 2) are the day of the month. The last digit identifies the year the block was cast.
  • Production Date Code
    F129

    • F=June
    • 12=12th of the month
    • 9=1969

    2. Block casting number. This is found on the distributor pad for 1964, 1965, 1966, and the first part of the year in 1967. Then midway through 1967 it was moved to the back of the block behind the number 8 cylinder.
    Year     CID         Casting Number
    1964     389         9773155
    1965     389         9778789
    1966     389         9778789
    1967     400         9786133
    1968     400         9790071
    1968     400         9792506
    1969     400         9790071
    1969     400         9792506
    1969     400         9792968
    1969     400         545887
    1970     400         9799914
    1970     400         9799915
    1970     400         481708
    1970     455         9799140
    1971     400         481988
    1971     455         483677
    1971     455         485428
    1972     400         481988
    1972     455         485428
    1973     400         481988
    1973     455         485428
    1973     455         490132
    1974     350         488986

    3. The Engine Code can be found on the front of the engine block. It is stamped on the right hand bank on a machined pad. The engine code is directly below the engine production number.
  • Engine Code
           123456
             WS
         22P100001
    		•
    • 123456 -Engine Production Number
      (No correlation to the Vehicle VIN)
    • WS -Engine Code
    • 22P100001 -Engine VIN Code
      added late 1967. (2=Pontiac, 2=Model Year, P=Pontiac Assembly Plant, 100001=Last six numbers of the car VIN)
    Engine Code Legend
    • Letter Code -Two letters stamped on front of block that make up the Engine Code.
    • CID -Cubic Inch Displacement
    • HP -Horse Power
    • Trans -Transmission installed (Auto=Automatic, Man=Manual)
    1964 Letter CodeCIDHPTrans
    76X 389 348 Man
    77J 389 348 Auto
    78X 389 325 Man
    79J 389 325 Auto

    1965 Letter CodeCIDHPTrans
    WS 389 360 Man
    WT 389 335 Man
    YR 389 360 Auto
    YS 389 335 Auto

    1966 Letter CodeCIDHPTrans
    WS 389 360 Man
    WT 389 335 Man
    WV 389 360 Man
    WW 389 335 Man
    XE 389 335 Auto
    XS 389 360 Man
    YR 389 360 Auto
    YS 389 335 Auto

    1967 Letter CodeCID HPTrans
    WS 400 360 Man
    WT 400 335 Man
    WV 400 360 Man
    WW 400 335 Man
    XL 400 255 Auto
    XM 400 255 Auto
    XP 400 360 Auto
    XS 400 360 Man
    YR 400 360 Man
    YS 400 335 Auto
    YZ 400 360 Auto

    1968 Letter CodeCIDHPTrans
    WS 400 360 Man
    WT 400 360 Man
    WY 400 360 Man
    XM 400 265 Auto
    XP 400 360 Auto
    XS 400 360 Man
    XW 400 360 Auto
    YS 400 350 Auto
    YZ 400 360 Auto

    1969 Letter Code CID HP Trans
    WS 400 366 Man
    WT 400 350 Man
    WW 400 370 Man
    XP 400 370 Auto
    XX 400 265 Auto
    YS 400 350 Auto
    YZ 400 366 Auto

    1970 Letter Code CID HP Trans
    WA 455 360 Man
    WS 400 366 Man
    WT 400 350 Man
    WW 400 370 Man
    XP 400 370 Auto
    YA 455 360 Auto
    YS 400 350 Auto
    YZ 400 366 Auto

    1971 Letter Code CID HP Trans
    WC 455 335 Man
    WK 400 300 Man
    WL 455 335 Man
    WT 400 300 Man
    YC 455 325 Auto
    YE 455 335 Auto
    YS 400 300 Auto

    1972 Letter Code CID HP Trans
    WK 400 250 Man
    WM 455 300 Man
    WS 400 250 Man
    YB 455 300 Auto
    YC 455 250 Auto
    YS 400 250 Auto
    YT 400 250 Auto

    1973 Letter Code CID HP Trans
    WK 400 230 Man
    WP 400 230 Man
    WS 400 230 Man
    X5 400 230 Auto
    X7 455 250 Auto
    XE 455 250 Auto
    XK 400 230 Auto
    XL 455 250 Auto
    XM 455 250 Auto
    XN 400 230 Auto
    XX 400 230 Auto
    Y3 400 230 Auto
    Y6 400 230 Man
    YA 455 250 Auto
    YC 455 250 Auto
    YD 455 250 Auto
    YF 400 230 Man
    YG 400 230 Man
    YK 455 250 Auto
    YS 400 230 Auto
    YT 400 230 Auto
    YY 400 230 Auto
    ZA 455 250 Auto
    ZC 455 250 Auto
    ZS 400 230 Auto

    1974 Letter Code CID HP Trans
    WP 350 200 Man
    YS 350 200 Auto
    YP 350 200 Auto
    ZP 350 200 Auto




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