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2 bolt or 4 bolt

Discussion in 'The Garage' started by K5Dan, Oct 8, 2003.

  1. K5Dan

    K5Dan 1/2 ton status

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    can someone explain to me how I can tell the difference between a 2 bolt or a 4 bolt?also which in your opinion is stronger ? thanks in advance /forums/images/graemlins/thumb.gif
     
  2. Don

    Don 1/2 ton status

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    Without pulling the pan, on a smallblock 350, most 3970010 casting number block's are 4 bolt main's. 4 bolt's really are'nt that great at being stonger than a 2 bolt block. Because of the outside bolt's bore's are in the webbing of the main bearing saddle's. /forums/images/graemlins/grin.gif
     
  3. heavy4x4

    heavy4x4 1/2 ton status

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    Do you mean, "tell the difference by looking at the engine externally?" As far as I know...there's no way to do that. You need to pull the oil pan. Then, once that's off, look at the main bearing caps. If there are 4 bolts holding each one into the block, it's a 4-bolt-main block and if there are 2 bolts, then it's a 2-bolt-main block.

    As for which is stronger. If I were to buy a block, I'd get the 4 bolt just because I like the added security of over-building everything. BUT, there is nothing wrong with a 2 bolt engine so long as it doesn't see RPMs much over 5 grand.
     
  4. wrathORC

    wrathORC 1/2 ton status

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    A splayed-main 4 bolt is stronger than a regular 4 bolt which is stronger than a 2 bolt.

    The difference is in the center three main caps.

    The easiest way is to look at the casting number which is behind the driver's side cylinder head on top of where the bellhousing bolts to.

    I've noticed recently that the 4 bolt main blocks usually have a threaded hole at the top of the bellhousing. I don't know if this is a theme or just a freak coincidence.
     
  5. K5Dan

    K5Dan 1/2 ton status

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    hey thanks guys !this all started when me and a nieghbor where tearing down the engine out of my 73 k10 casting number 397010. I said it's a four bolt because the main caps .he said no it was a 2 bolt because the ones on the ends have two bolts.so i pulled him inside and made this post (hoping i was right).after his supposedly meachanic step dad also said it was a two bolt. /forums/images/graemlins/thumb.gifthanks again! where else can you go at 8ish at night to ask ?'s like these and get the right answers /forums/images/graemlins/thumb.gif
     
  6. Confedneck

    Confedneck 3/4 ton status

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    379010 blocks=4 bolt main blocks...have one in the garage waiting to become a 385 stroker one of these days...
    4 bolt is stronger than 2 bolt
    if you splay a 2 bolt block and make it 4 bolt, it is now stronger than standard 4 bolt...make a 4 bolt a splayed 6 bolt...and you wont break lol
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    379010 blocks=4 bolt main blocks

    [/ QUOTE ]

    Not all of them nastyz28 casting #'s

    (BTW, I believe you mean 3970010)

    *TRUCK* 350's are almost universally 4 bolts (which is why suffix codes are about the best engine codes to use), I have yet to find one that isn't, but I'm sure they exist.
     
  8. Confedneck

    Confedneck 3/4 ton status

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    yes i do mean 3790010.. and i meant truck blocks as this is primarily a truck/k5 site...
    /forums/images/graemlins/grin.gif but thanks for clearing it up... /forums/images/graemlins/thumb.gif
     
  9. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    But arent pre-'77 i think, 2 bolts strong enough because they have nickle in the block?
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    That nickel thing has never been proven. You've heard it was a year thing, others say its related to the "010" and "020" cast into some of the blocks.

    No literature or tests have yet surfaced to prove any theories as to block strength. Oldsmobile motors have the same myths surrounding them based on year/nickel/tin content, with the same *proof*. None.
     

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