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Hypereutectic Piston Question...

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Old Dec 1, 2010 | 12:40 PM
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Default Hypereutectic Piston Question...

Everywhere I look I find info that says not to bore/hone the LS1 block more than .010" (.25mm). So why do Keith Black & Sealed Power / Speed-Pro offer hyper pistons up to .040" (1mm) oversize? Is the .010 rule-of-thumb only for nitrous or FI applications? What do you guys think?
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Old Dec 1, 2010 | 02:54 PM
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Part number? You may be looking at pistons for an iron 6.0L block.
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Old Dec 1, 2010 | 06:23 PM
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Originally Posted by KCS
Part number? You may be looking at pistons for an iron 6.0L block.

^^^^ Where the smart $$$$ is.........
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Old Dec 1, 2010 | 08:45 PM
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KB #3498HC - page 65 from the 2009 catalog - here

Rock Auto has Sealed Power (Speed-Pro) #H868CP for an '02 Camaro - here

Both show .25mm, .50mm, .75mm, & 1mm oversize.

Summit sells both:

http://www.summitracing.com/parts/UEM-3498HC-1-0MM/

http://www.summitracing.com/parts/STL-H868CP75MM/

Last edited by hiltsy855; Dec 2, 2010 at 05:40 AM.
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Old Dec 2, 2010 | 09:32 AM
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Weird, I've never seen that before. Thanks for the links though.

I would call and see what they say.
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Old Dec 2, 2010 | 12:36 PM
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Originally Posted by KCS
Weird, I've never seen that before. Thanks for the links though.

I would call and see what they say.
I called and the KB tech guy said he didn't know why they offered those oversizes. Very strange indeed.
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Old Dec 3, 2010 | 01:26 PM
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GM recommends the '97 to '98 LS1 blocks be honed only 0.004" while '99 and later can only be bored 0.010".
However, since GMPP themselves have stated that some 5.3 blocks can be bored to 4.00", then maybe those other pistons would be fine for iron block mods?
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Old Dec 3, 2010 | 01:43 PM
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Originally Posted by Isolde
GM recommends the '97 to '98 LS1 blocks be honed only 0.004" while '99 and later can only be bored 0.010".
However, since GMPP themselves have stated that some 5.3 blocks can be bored to 4.00", then maybe those other pistons would be fine for iron block mods?
You're probably right. I've heard of LS2's going out to 4.030" but I can't imagine that that would be something that would live long with a considerable amount of power. An iron 5.3L block would probably be fine at that bore. The hypereutectic piston would probably have problems before the cylinder would.
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Old Sep 23, 2018 | 10:16 AM
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Originally Posted by hiltsy855
Everywhere I look I find info that says not to bore/hone the LS1 block more than .010" (.25mm). So why do Keith Black & Sealed Power / Speed-Pro offer hyper pistons up to .040" (1mm) oversize? Is the .010 rule-of-thumb only for nitrous or FI applications? What do you guys think?
I know they say don’t bore it out... but the previous owner of my car didn’t listen... my car has the h868cp+.50mm (.020) over bore and I’ve been spraying It for a few months (100-150 shot) and she’s still doing ok... tbh I was kinda bummed when I saw that the pistons were +.5mm because of what everyone says about not boring the ls1. My car runs 11.2@123. I’m either gonna get into the 10’s or blow it up cuz I’m about to spray a bigger shot next time out
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