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boreing a ls to 82mm?

Discussion in 'Engine Building' started by erebunicrx, Dec 21, 2004.

  1. erebunicrx

    erebunicrx my name is Dale

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    is it safe to bore to 82mm on stock ls sleves? im reving to about 8500 and will see about 200 whp.
     
  2. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    I would go to 81.5mm max. You won't really gain that much displacement going out another .5mm.
     
  3. 99SiRidinLow

    99SiRidinLow Senior Member

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    You should be good... I'll be boring my b16 to that here soon... Only because thats the smallest size the piston i want comes in :blink:
     
  4. hcivic.com

    hcivic.com Senior Member

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    why bore that big just go as big as you need to clean up the walls the extra .5 mm don't do a hell of a lot
     
  5. erebunicrx

    erebunicrx my name is Dale

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    b/c for the same money for the machine work and pistons i will be gaining hp. i will be ok if i post it right?
     
  6. StyleTEG

    StyleTEG Senior Member

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    A little bit of displacement goes a long way.

    Keep in mind the difference in torque between a B18B and a B18C1/5

    Thats a difference of 37cc's

    Going from 81.5mm to 82mm is almost as big a change.

    I don't know if I would rev past 8000rpm on stock sleeves opened up that much, but I wouldn't say boring half a mm doesn't do much.
     
  7. brian11to1

    brian11to1 Senior Member

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    Boring the LS to 82mm makes it a 1.88L engine ;)

    Also if you use 82mm LS pistons it raised compression. Im not sure if they make PR4's that big though... I know 81.5's are made.
     
  8. erebunicrx

    erebunicrx my name is Dale

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    im going with somthing like wiseco or je's. i want arond 12:1 comp B). need some kinda compression for the 404's
     
  9. StyleTEG

    StyleTEG Senior Member

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    Thats going to undercam the motor like crazy. 11.6:1 CR is the sweet spot for 404's.
     
  10. erebunicrx

    erebunicrx my name is Dale

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    where and how did you find that out? i've been trying to find out what the best comp was for awhile but was not sure
     
  11. StyleTEG

    StyleTEG Senior Member

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    When you change your cams or your compression you change cranking pressure.

    Since the intake cam keeps the intalve valve open slightly passed bottom dead center, some compression is bled off during the compression stroke. The result is less compression than your static compression (this is refered to as dynamic compression).

    Because of this you need higher compression with more aggressive cams, more compression is bled off.

    The sweet spot in general is between 20% - 25% INCREASE in cranking pressure over stock. Losing cranking pressure is a bad thing. Anything above 25% and the resistance is going to slow down the pistons as it reaches TDC, and it will blunt your top end gains.

    I also have 404s, so I basicly did some calculations with a dynamic compression calculator to find out what would be a 25% increase in cranking pressure over stock.

    Turns out 11.6 - 11.7:1 is
     
  12. erebunicrx

    erebunicrx my name is Dale

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    awesome thanks for the info. do have any ideas for the right pistons?
     
  13. brian11to1

    brian11to1 Senior Member

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    Anything that's like 11.5:1 - 11.6:1...
     
  14. erebunicrx

    erebunicrx my name is Dale

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    ummm.. how about a brand.
     
  15. brian11to1

    brian11to1 Senior Member

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    Ooops, check IB Spec
     
  16. erebunicrx

    erebunicrx my name is Dale

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    they dont list any for ls
     
  17. brian11to1

    brian11to1 Senior Member

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    As long as they are for B series you can use em. And as long as it fits your bore, you can use them.
     
  18. brian11to1

    brian11to1 Senior Member

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  19. erebunicrx

    erebunicrx my name is Dale

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    what about them fitting on the rods?
     
  20. brian11to1

    brian11to1 Senior Member

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    Check out IB's rod selection for the LS
     
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