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Rock pistons and cyl wall question

thedsmguy

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Joined
Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
I have a chance to buy a "shop" rebuilt factory spec bottom end for a pretty cheap price. Question is, are "rock" pistons worth a crap and one of the cyl walls has a up/down "scratch" in the cyl wall, if you run your fingernail over it it will catch lightly. I would think that this would still run fine the motor spins freely etc. Any input would be awesome.

Thanks.
 

The_Big_Weave

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Joined
Feb 26, 2009
Messages
390
Location
Rapid City, SD
If it was rebuilt they should have bored and honed the cyl and you should not feel anything it should be smooth.
 

TylerAdamson

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Joined
Dec 26, 2007
Messages
1,034
Location
Iowa City, Iowa
If you're fingernail is catching it then it wasn't machined properly. I would not run the motor
 

usually when boring a block the boring bar leaves a vertical line in the cylinder. it should go away when the cylinders are honed. if its still visible, and worse, you can feel it, then the machine shop messed up.
 

alansupra94

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Mar 3, 2010
Messages
1,909
Location
Wayne,NJ
You should definitely not be feeling anything on those walls. Seeing the crosshatching is a different story.
 

Muskrat

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Jun 13, 2004
Messages
2,107
Location
Lexington, KY
^1 on what's been said.

1) It's a stress riser.

2) It's a heat riser.

When/if that block fails, I bet it cracks in that groove. I'd stay away from it. No reason to buy a questionable block, unless you plan to bore it out anyway.
 

thedsmguy

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Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
Ok.. The weird thing is that its not a true strait up and down line. Sorta goes sideways a little almost like it was put(or happened) after it was honed etc. I'll just pass on it I guess.
 

thedsmguy

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Joined
Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
I pulled the piston out of that block today. The bottom (oil scraper) ring had its "middle" part basically overlapping itself. I went to a machine shop and they suggested emmory cloth and a ball hone and let it rip.

Anyone see any problems? The scratching really wasn't super deep.
 
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