Problems from scored cylinder walls?

[DartVadar]

So a while ago me and my cousin pulled apart a 'new' ford 302 that had a weird vibration, and noticed some light vertical scoring/scratching on the cylinder walls. This reminded me that I've seen it a few other times as well, It was like that on my 360 when I took it apart to rebuild it as well. This made me wonder how bad or not bad these scratches are.

But my main question is how much vertical scratching/scoring is too much? and what would happen if you ran an engine with a scratch that would catch your nail vs one that was light and you could only see?

I noticed that I had some very light vertical scratches in my 360 when I was rebuilding it (bored and honed) after I hand turned the motor over a few times when I put the rings and pistons in, but could only see them under the right light, and could not feel them at all. The rings were set to the correct gap and I made sure to get rid of any burrs left after filing the rings.

Are these minor scratched any reason for concern? How bad would they have to be to cause noticeable oil blue smoke and loss of compression?

 

[krazykuda]

If you can catch it with a fingernail, then worry about it.

 

[moper]

usually those scratches are from debris being caught between the skirts and the cylinder walls. Sometimes from assembly, sometimes environment. That scoring is just like having the wrong wall finish. It damages rings, ruins ring seal, stops rings from rotating, and basically loses sealing and efficiency and power. Might not be fatal, but there's always an affect.