New engine build help..stag

[Gord53]

I'm hoping some pro engine builders can advise on this.
So I have a stag engine I'm rebuilding..block has been bored +40..and faces skimmed.
Crank reground. New pistons that came with rings fitted.
New little end bushes fitted and honed and con rods fitted to pistons.
All this has been done by same machining company.
I've fitted crank and pistons ensuring rings are staggered,now I have noticed scoring running up the bores from the ring gaps.enough that a finger nail can feel it.
Question is should I have to gap the rings even if supplied fitted to pistons......or is there another issue maybe.thanks

[tapkaJohnD]

It's been rebored to +40, an d there are STILL scores in the bores? That you can feel with a fingernail?? Sack the company who did the work, get it rebored to +60, invest in +60 pistons. Else you will never get decent compression.

THEN, yes, gap your rings, always.

And, staggering the ring gaps is not necessary. Rings rotate in use at about 100th of the revs, but not equally. There's no point in staggering!

John

[stevieturbo]

Pictures

[Arnold Cunningham]

tapkaJohnD said:

And, staggering the ring gaps is not necessary. Rings rotate in use at about 100th of the revs, but not equally. There's no point in staggering

I’ve always wondered this. It seems obvious that they may, unless a 2 stroke which has them pinned. But the last engine I built was quite particular about the offsets.

Edited by Arnold Cunningham on Wednesday 26th April 21:19

[TwinKam]

Are you saying that the new rings have caused this scoring during recent assembly, or that the boring to +040 hasn't eradicated previous scoring?

[Boosted LS1]

There will be a score in the bore from the boring honing process but it's not something you can feel with a finger nail. It's more of a witness mark. I deburr the piston ring ends as a matter of routine.

Op did you use a proper tool to insert the pistons into the bores? If not the oil rings maye have caused scoring. Does the score start from the top of the bore? If so, remove the pistons and start again.