Rock pistons and cyl wall question

[thedsmguy]

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]

If it was rebuilt they should have bored and honed the cyl and you should not feel anything it should be smooth.

 

[TylerAdamson]

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]

You should definitely not be feeling anything on those walls. Seeing the crosshatching is a different story.

 

[Muskrat]

^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]

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]

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.