I bought a used B18C5 block with 20k miles and it has a few vertical marks on the cylinder walls.They are about 1" in length and each cylinder seems to have them.I can't feel them at all with my finger or fingernail.You can still see the crosshatching perfectly..What's the dealio

 

You got pics??

 

The short answer is "no". If you can get your fingernail "caught" in them, then that's bad. If it's just barely, and they don't run the entire length of the cylinder, you MIGHT be alright with some light honing, but I wouldn't chance it myself... it's an escape route for oil just waiting to happen. I'd be looking extra carefully for other signs of abnormal wear, and would prolly bore it out .025 and put in oversize pistons. Good luck.

 

Every torn down motor I've seen has marks similar to what you're describing. If they're so light you cant feel them, then it should not be a problem. If I was rebuilding the motor, I would run a hone through the cylinder to break the glaze on the cylinder walls and allow the new rings to seat properly. This might remove those LIGHT grooves as well. If your cranking compression is within spec, I wouldn't worry about it for a street-driven motor. If you're an all out racer with a last name like Papadakis, I'd keep it to a tighter wear tolerance

 

FYI papadakis ran 8.12 at like 180mph last weekend. Almost into the 7's.

If the lines dont run the length of the sleeve, its probably not a big deal. And if you cant grab it with your fingernail you should be ok. Most motors i see have this same wear. They work fine as well.