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396 or 402????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Stomp, May 20, 2002.

  1. Stomp

    Stomp 1/2 ton status

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    Is there anyway to tell the difference between the two???

    I got my big block but the guy couldn't remember which it was. I looked up the numbers on the internet and came up with 1969-1972 396/402.

    Any Ideas???
     
  2. 88streetblaze

    88streetblaze 1/2 ton status

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    a 402 is just a 396 that's been bored .030 over. I belive that Chevy started doing that in '70, but they still called it a 396.
     
  3. Stomp

    Stomp 1/2 ton status

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  4. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I think the 396 was called the 402 in '72. They are just a .030 over bored 396. Same motor, same specs, etc., just a larger bore for the pistons.

    I can't remember exactly what year they started the 402 and ended the 396 configuration. Somewhere between '71 or '72 I believe.
    You still see the '70 Chevelle's with the 396 emblems on the fenders, so, that's got me believing the 402 started in '72. /forums/images/icons/wink.gif
     
  5. Stomp

    Stomp 1/2 ton status

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    so make sure I get.030 over pistons and rings
     
  6. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Check the back of the block, on the top part where the bellhousing bolts to and see if you can view the year of the block. It will be on the passenger side, right behind the head.
    If you can get the year of it, that will let you know whether you can get the .030 pistons or not.

    Now if it were me and I had a 402, and it needed to be bored out, you would need .060 over 396 pistons or .030 over 402 pistons. Make sense?

    That's why I can't remember exactly what year the 396 stopped and the 402 started.
     
  7. Stomp

    Stomp 1/2 ton status

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    the tag says 70
     
  8. Stomp

    Stomp 1/2 ton status

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    I pm'ed you guy
     
  9. 91K5

    91K5 1/2 ton status

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    The 396's started getting bored out to 402 midway through 1969, but kept referring to them as the "396" until '71, in '72 they actually called them the "400-4", as opposed to the 400 small block which was the "400-2". I have a '72 Chevelle with the 402, you wont be dissapointed with the power.
     
  10. Stomp

    Stomp 1/2 ton status

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    So after all that has been said. Basically I need to measure the cylinder to see what it is
     
  11. 91K5

    91K5 1/2 ton status

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    Since your engine stampings denote a '70 model, it would be a 402 cube motor. Double checking the bore would be a good idea since it might have been rebuilt at sometime though. The stock bore should be about 4.125" for a 402.
     
  12. Stomp

    Stomp 1/2 ton status

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    Thx K5, That was my next question lol
     
  13. Dunc03

    Dunc03 1/2 ton status

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    What I've heard numerous times, is that the 396 was actually a 402 from the beginning. It was only called 396 for marketing purposes. I heard that on a classic car show, but have no sources other than that, so take it for what it's worth.
     
  14. madmike

    madmike 1/2 ton status

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    Go to www.Mortec.com. That sight lists casting numbers and applications for everything, that might help you. I don't know how to do the "clicky" thing...
     

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