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2 bolt or 4 bolt main

Discussion in 'The Garage' started by wraenking, Jun 29, 2004.

  1. wraenking

    wraenking 1/2 ton status

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    just found out by looking up the casting number on the engine i got that it is a 2 bolt main. can i still use this?

    the casting number is 3970010 and it says it could be 2 or 4 bolt, and 327 or a 350. ahhhhhhhhh

    thanks

    tom
     
  2. big pappa b

    big pappa b 3/4 ton status

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    Re: 2 bolt main

    Can you use it? Can you explain a little more? Do you have a 4 bolt main now and want touse the new 2 bolt main..using just the block or what??
     
  3. wraenking

    wraenking 1/2 ton status

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    Re: 2 bolt main

    im confused because i looked at another site and that casting id could be 2 or 4 bolt. so i dont know what the hell i have.
     
  4. big pappa b

    big pappa b 3/4 ton status

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    Re: 2 bolt main

    only way to tell for sure is to drop the pan
     
  5. wraenking

    wraenking 1/2 ton status

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    Re: 2 bolt main

    ok, and what do i look for, and am i screwed if it is a 2 bolt
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 2 bolt main

    No, you're not screwed if it's 2 bolt. There really is no reason to have a 4 bolt main engine in a K5 unless you're mud racing or something.

    305s were installed in MANY trucks for a long time. ALL of them are 2 bolt mains and they work just fine.

    4 bolt mains are only necessary for heavy duty trucks (3/4, 1 tons, etc) and for high RPM blasts. And even then, splayed mains are preferred to factory 4 bolt mains for the most extreme of engines.

    For the 400 SBC, the desireable block is the 2 bolt main one, too.

    I wouldn't fret at all about having a 2 bolt main engine (if I had one). There's absolutely nothing wrong with a 2 bolt main.
     
  7. wraenking

    wraenking 1/2 ton status

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    Re: 2 bolt main

    but is it a 350? my buddy said it was. said it was bored over .30 and everything. i just ripped out my 205, and i really wanted this "350"


    lol
     
  8. big pappa b

    big pappa b 3/4 ton status

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    Re: 2 bolt main

    the casting # you gave is for sure a 350. I've owned a few with that same #
     
  9. wraenking

    wraenking 1/2 ton status

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    Re: 2 bolt main

    ok, but i looked it up and it also listed as 327?

    sorry to be a pain, im just freaking out here. lol
     
  10. POWERMAD

    POWERMAD 1/2 ton status

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    Re: 2 bolt main

    Is it in yer rig?
    On a stand?
    What is it you are lookin to build?
    There is nothing wrong with a mild SBC with 2 bolt mains.
    Start strokin it then ya can start lookin for one with 4 bolt mains..
    .
    Most likely it is a 350, I just went through this with my hoopty.
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 2 bolt main

    [ QUOTE ]
    ok, but i looked it up and it also listed as 327?

    sorry to be a pain, im just freaking out here. lol

    [/ QUOTE ]

    327 and 350 are the same block. It is the crankshaft and pistons that make one different from the other.

    Without running the numbers on the crankshaft it'd be impossible to know which one you've actually got. I'd say you probably have a 350.
     
  12. wraenking

    wraenking 1/2 ton status

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    Re: 2 bolt main

    ok, thanks guys. the fact that the my friend said its a 350 bored .30 over, i ll go with it, its just when i looked it up, i panicked. i want to get it in the blazer by the weekend, so wish me luck!!
     
  13. POWERMAD

    POWERMAD 1/2 ton status

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    Re: 2 bolt main

    Good Luck.... /forums/images/graemlins/waytogo.gif
     
  14. bigburban383

    bigburban383 1/2 ton status

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    Re: 2 bolt main

    [ QUOTE ]
    ok, and what do i look for, and am i screwed if it is a 2 bolt

    [/ QUOTE ]

    Just buy some new ARP studs and call it good. No worries, you aren't running a supercharged alcohol dragster, are you?
     
  15. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: 2 bolt main

    Using a 2 bolt block shouldn't be a problem. My mildly built 406 is a 2 bolt main and I haven't had any problems.

    Also you can always get the Milodin splayed caps and make it stronger than a stock 4 bolt main....
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: 2 bolt main

    Whats the suffix code?

    Passenger side, just forward of the cylinder head, looking down on engine as it would be installed in the truck, on the flat pad, stamped in.

    If it turns out to be a truck block, (suffix code will tell) you can pretty much be guaranteed it's a 4 bolt, although I'm sure there are a few that weren't.
     
  17. sled_dog

    sled_dog 1 ton status

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    Re: 2 bolt main

    yeah I look for 2 bolts now cause you can just go to milodon splayed and be better off.
     
  18. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I have seen my share of that casting number, all but one had 4 bolt mains. I had the casting number book, loaned it and never got it back. I remember it being 72-76 truck AND cars with optional engine ( like ss's and s3's or A/C or towing equipped ) /forums/images/graemlins/k5.gif
     
  19. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Mines a 2 bolt. I thought pre '77 blocks had nickel in them which made them stronger anyway.

    Think about, how often do you see a block cracked in half? /forums/images/graemlins/dunno.gif
     
  20. 88Silverado

    88Silverado 1/2 ton status

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    If im not mistaken, 4-bolt mains didnt appear until the 70's. There were alot of very fast cars in the 60's that ran 2-bolt mains. If you dont plan on running it over 6500-7000 RPM's as a wild motor, the 2-bolt will work fine. If you are going to spin it high RPM's, I would spend the extra money and have it balanced. Ive seen a few blown motors but never seen one drop the cap due to a main or rod bolt failure unless it extremely high performance. Mostly broken rods, broken crank, spun bearings, etc.
     

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