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Thread: 396 402

  1. #1
    Senior Member SENIOR BUILDER
    Join Date
    Nov 2007
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    indiana
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    123

    396 402

    what is the actual difference in the two motors?
    if something goes wrong there is always the cooler!!!

  2. #2
    Senior Member RACING JUNKIE
    Join Date
    Jan 2006
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    La.
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    2,890
    .030 over bore in the cylinders, GM did this with a few blks in the late 70's which were out of tolerance for the 396" bore.

    Zip.

  3. #3
    Senior Member SENIOR BUILDER
    Join Date
    Nov 2007
    Location
    indiana
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    123
    so can a guy order a rebuild kit for a 396 just 30 over rings? mains a nd rod journals are the same
    if something goes wrong there is always the cooler!!!

  4. #4
    Senior Member DYNO OPERATOR
    Join Date
    Jan 2004
    Location
    central Illinois
    Posts
    459

    396 402

    In 1970 GM had several 400 inch engines. The 396 was bored .030" to be compatible with the sister divisions 400 engines. I had a new 1970 Nova SS 400/402 BBC 375 horse 4 speed in the fall of 1969. I remember when shopping for engine parts at the Chevy dealer this always came up as a question of the difference between the 400 SBC and the 400 BBC.

    Anyway, a 402 uses 396 +.030" parts as its standard parts. If you are rebuilding and increasing a 402 +.030" then it is a 396 +.060 listing that you would use.

    There are people in Super Stock that are taking 454 blocks and sleeving them down to 396 +.090" over bore to use as a 402 +.060 legally. In fact there is one listed on RJ now like that. I also have a relative who races a 1970 Chevelle SS with that combo too in a NHRA class.

  5. Racing Junk


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