How much can a 350 be safely bored?

Discussion in 'Engine Topic' started by Rajin, Aug 6, 2010.

  1. Rajin

    Rajin Veteran Member

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    Jun 28, 2009
    Kelowna, BC
    On a local classified site, a guy is trying to sell a 4 bolt main, 350 for $100. Casting Number: 3970010. He says that it's currently 30 over, but needs to be honed to 40 over.

    Would it be possible to use this block to build a forced induction motor if it was 40 over?
     
  2. z28rod

    z28rod Veteran Member

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    Apr 30, 2009
    hopewell junction,ny
    60 is about it on a gm stock block.
     
  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,372
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    Nov 4, 2004
    Ringgold, GA
    Well you won't hone it to .040 over and while most 350 blocks can be bored to .060, it's a good idea to have it checked first as core shift can cause thin spots.

    If you're planning to go forced induction, certainly have it checked out.
     
  4. badazz81z28

    badazz81z28 Veteran Member

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    May 4, 2001
    Las Vegas, NV
    I dont think I would buy a block already .030 over...I would keep looking. My block was .030 over and when I tore it down one of the cylinders was grooved badly...Would not clean up. If you do buy it, tear it town and get it looked at first. Get a Re-build guarantee...
     
  5. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

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    It depends on what you mean by FI.
    If you mean hardcore, real power type combination, then you have no business using any stocker.
    If you mean barely over stock, a hundred or 2 HP, then may be??

    If he's a stand up guy and not trying to pull anything, he should let you pay to have it checked??



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  6. Rajin

    Rajin Veteran Member

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    Jun 28, 2009
    Kelowna, BC
    I was thinking twin turbo, 10 - 15 PSI. Nothing incredibly hardcore. The car will be street driven regularly.

    I'm thinking 300 - 400 hp at the rear wheels.
     
  7. z28rod

    z28rod Veteran Member

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    Apr 30, 2009
    hopewell junction,ny
    should be fine.
     
  8. NYH1

    NYH1 Veteran Member

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    Feb 27, 2010
    Central New York
    The 350 (#3970010) that came in my car was .040" over. I planned on having it bored .060" over which my machinist said was fine as long as it sonic tested out ok. We never made it that far. I dropped the block off and he noticed right away when he started cleaning it that there were two cracks that some @$$ hat, more then likely the guy I bought the car from tried hiding with epoxy.

    He had another 350 (#3970010) block that was already .030" over when he got it and just needed to be cleaned up a tad. So he sonic tested it and bored/plate honed it to .040" over (said we could have gone .060" over if we wanted too) and I was completely fine with it. Mainly because the block was coming from him and everything checked out fine or he wouldn't have thought about using it if it didn't. I wouldn't buy or at least spend to much money on block that was already bored. Unless of course I was guarantied my money back if the block did pass a sonic test. Or if it was from a reputable machine shop, I'd still take it to my guy and have it checked though. :bowtie:
     
  9. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    Jun 22, 2003
    Endicott, NY
    IMHO, I'd pass on it ESPECIALLY since you want to put "forced induction" (blower?) on it. IMHO, the MORE block you have (standard bore to maybe .030" over) the better.
     
  10. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

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    Can you even keep a twin turbo to 3-400 HP and why spend all that dough for such a low powered combination???


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