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What's the difference between .030 and .040??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BLzr4x4ngkid, May 24, 2000.

  1. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    What\'s the difference between .030 and .040??

    Besides the #'s, what's the difference. How much horsepower, etc. will I gain with either. I don't know if I should go with the .030 or the .040. I'm going to rebuild 350 this summer and want to bore it, but now I have to decide. Thanks

    Alex
    Wichita, KS
    [​IMG]What me get stuck? NEVER!!(Famous last words)[​IMG]
     
  2. walrus101

    walrus101 Registered Member

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    Re: What\'s the difference between .030 and .040??

    the cylinders are bored out .030 or .040 of an inch; depending on how bad the walls look. different opinions will be out there. i would go .030. reason is, down the road you can rebuild again; with plenty of walls left. i believe the max. is .060. as you bore out you are making the walls thinner; which can lead to over-heating, and other possible problems. h-power will not be that big of a difference. you will be able to use bigger pistons. i am assuming that you don't want a huge power horse. for rock-crawling and tons of h-power usualy led to lots of broken axles and parts, but for mud you might want it. you can build it how you want it though.

    walrus101

    goo goo gaju
     
  3. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    Re: What\'s the difference between .030 and .040??

    I don't rock crawl, but I tend to find myself in mud all the time. I have even been caught in those precarious situations where I'm pulling someone out of the mud as well. My dad and I both don't want to go above .040, so we'll find out some more info and let you guys know what's going to happen. Thanks again.

    Alex
    Wichita, KS
    [​IMG]What me get stuck? NEVER!!(Famous last words)[​IMG]
     
  4. CBLAZER81

    CBLAZER81 1/2 ton status

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    Re: What\'s the difference between .030 and .040??

    Walrus is right.Do as little boring (oversizing)as you can get away with,depending on the condition of the cylinder walls.Sometimes it's even possible to hone out the cylinders,if they're not scrapped up too bad,without going oversized at all.(I think-I'm no expert by any means)
    Whatever you do,remove the least amount of material possible from the block.As Walrus said it gives you a better chance of getting a future rebuild out of your block.And cooling could become a problem.
    Good luck

    <font color=red>Wanna'keep wheelin? Get involved!
    Check the "Land Use" section of this board.</font color=red>
     
  5. Mudzer

    Mudzer 1/2 ton status Author

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    Re: What\'s the difference between .030 and .040??

    Send me an email with your specs and exact cam profile and I can give you a ballpark on my Dyno program. Then I can offer suggestions about what you can do to make more power.


    <font color=red>Mudzer</font color=red>
    1978/91 K5 Blazer
     
  6. BIGRIG

    BIGRIG 1/2 ton status

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    Re: What\'s the difference between .030 and .040??

    .040
    -.030
    --------
    .010......SORRY I COULDN'T RESIST! :)


    MY DRINKING TEAM HAS A FOUR WHEELING PROBLEM!
     
  7. SnakeEyes

    SnakeEyes Registered Member

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    Re: What\'s the difference between .030 and .040??

    Yeah, me too! I'm weak! So "BOUT 0.10!!"
    OK, got that out of my system1
    Good machining practices always tell you to bore the MINIMUM needed to clean up the cylinder walls. A competent machinist can tell you how much to bore to get the wave out, If he can’t he's not competent and you should be somewhere else with your money and your block. If that sounds harsh think about being in the middle of nowhere when that rod end launches through the side of your block and the machinist is home drinking beer! Don’t get it punched until you have handed the pistons to your machinist. This will allow him to bore and fit the pistons down to the clearance called for by the piston manufacturer. This will get YOU there in 1 trip rather than 2 trips. The machinist can also complete the bore in 1 operation rather than 2 or 3 operations. Always good practice! When he hands you back your block and pistons each piston will be labeled to fit in the appropriate hole. If it ain’t, he didn’t do it right!. Check to make sure he’s a Chevy man and numbered the pistons in the Chevy manner. I once had a Ford machinist hand me back pistons for a Chev numbered using the Ford conventions! Could have been embarrassing and expensive for both of us!
    Good luck with this!!
     
  8. Captkaos

    Captkaos 1/2 ton status

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    Re: What\'s the difference between .030 and .040??

    I agree with those who said go the minimum amount. You aren't going to gain more power with .010". You will loose another rebuild later on down the road. Get the cylinders mic'd and get the pistons and bore the block.

    Chris Lucas
    http://www.wwisp.com/~captkaos
     

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