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B20 piston choice, what to do?

Discussion in 'Engine Building' started by becoming, Jul 10, 2006.

  1. becoming

    becoming Member

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    Hello all, was just wondering how big u can go on a stock sleeve B20 block? The reason i am asking b/c i have a friend that practically gave me a set of 84.5 mm pistons with the swain coatings already on them to go into a B20 block i got to do round track racing with so i am on a slight budget with that car b/c my street car is getting a new block too and don't want to sleeve 2 blocks at this time. So will i be "safe" to do a .020 overbore on stock sleeves?
     
  2. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Yes, 84.5mm is perfectly safe. It's within manufacturer specs too. Almost every B20 that is fitted with forged pistons in the stock sleeve is running an 84.5mm bore.
     
  3. becoming

    becoming Member

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    Well since you brought up manufacture's specs, Honda only recommends .25 mm over, as we both know is only .010, not .020 over. And when looking at there iron part of the factory sleeve, it isn't very thick...does this hurt me in the long run by possibley cracking due to heat?
     
  4. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Are you sure about that spec? Most of the Honda blocks allow .5mm over, and all the 81mm bore B series pistons (and the 75mm bore D series) are available from the factory in .5mm over.

    You'll be fine running 84.5mm. Like I said, almost all of the stock sleeve B20s are running 84.5mm bore- plus you're going to have lots of fun finding aftermarket forged pistons in 84.25mm. I ran over 45k miles on my B20 at 84.5mm with no problems, and I would have gone quite a bit longer if I didn't mess things up (no fault of the sleeve).
     
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  5. becoming

    becoming Member

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    Yea, if you go to Honda to buy pistons, you can get either standard, or .25 mm over. Which is .010....But then again, we may both be right, but i have never seen actual Honda pistons bigger than .25 mm over, not to say there isn't. But my original question is answered, Thanks. But since we are talkin about it, what kind of wall clearence did you run? And what kind of cams would you recommend being a crvtec...I am leaning towards the BC Spec 3's because of thier lower power band....but the crower stage 2's are an option too.
     
  6. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    I was thinking of the BC3 or BC4 (I think), also the Toda D- but I was shooting for 260whp, and my bore was 85.5mm on the last build.

    Wall clearances should be set up according to your piston manufacturer's specs. The last one I ran was at .0030 inches, and that was with forged CP pistons and ceramic coats from Swain Tech.
     
  7. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    bc3 cams will be way to mild for a b20vtec build. bc3s are more cam for stock motors. bc4s should do well. also look into some skunk2 pro1 or pro2
     
  8. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Wicked makes some nice cams too.
     
  9. becoming

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    I think i may end up goin with a gsr crank and rods to turn a few more RPM's, so i really don't know what cams to go with....especially since i want ITB's so bad i cant see straight!! But i have never heard of the wicked cams, but am starting to think i am gonna need way more than the BC3's in it...and i am sure i will end up with plenty of compression to run whatever i want....just don't want to get a set, then find out there are a totally better set i could be running afterwards! Thanks for all the help guys;)
     
  10. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    It's not worth it to switch to the GSR crank and rods. Stick with what you have- you'll make more power, and if you chose your bearings right, you won't have to worry about spinning through 8000rpm.
     
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