Piston ring "grooves" after honed cylinders.

[k.alle]

Hi.

Recieved my newly built bottom end today from the workshop that did the work.
As we loaded the block in the car i noticed that there were som marks in some of the cylinders.
Much like markings where the piston rings is TDC but "only" half moons.

Some of them is impossible to feel with the fingers and 1 or 2 is maybe 2 hundreds of an millimeter in "depth".

What i seek is knowledge, has anyone run with new rings and similar marks?

I know the theory about going first OD if having piston ring grooves.
But these are so minute so perhaps it doesnt matter in practice?

Im gonna snap a picture or to tomorrow and show you but id like to pick your brains until then.

Thanks

[pasbogdan]

Seems bores got just a slight honing to correct honing marks or out of round.
The wear of bores at tdc is usually more present to one side.That should be the reason you can see the"half moon".If the bores measured are in the specs for round,inside diameter and honing markings profile should be fine.

[k.alle]

Yeah well they had to hone because of the new piston rings.
So i shouldnt be overly worried?

They should be within spec since they assembled the bottom end.
It's been line honed at main bearings, balanced crank, skimmed mating surface to the head, weight matched internals etc.
So it would be an odd thing to leave out for them if needed.

[k.alle]

Picture of the bores as promised.uploadfromtaptalk1425749129134.jpg

[k.alle]

[ATTACH]52505[/ATTACH]

[SteveH]

That will be fine. Not perfect, but it shouldn't cause any issues. Mine were like that when I rebuilt my engine and it's been running for years since without any compression problems.

[Thuppu]

That will be fine. Not perfect, but it shouldn't cause any issues.

+1

[k.alle]

Thanks guys for your input. Its reassuring that there has been some practical experience with it.
Im gonna be able to sleep soundly now and move on

[pasbogdan]

Based on my experience that marks(especially on one cylinder) indicates 0.01-0.02 mm of wear.Considering new honing removing another 0.01-0.02 mm(on light honing) that will get to 0.04mm total wear measured diameter.That will mean neglectable circle length increasing so neglectable ring gap increase.
If your pistons were in good shape i can say that engine will work ok on stock/small upgrade power levels.What i will do,and it is good to do even on a new engine,wait until the engine warms up and pistons heat expand and abuse it after that point.
If you trust your services supplier get all mounted back in.If you do not,measure the bores and find out if the honing was a light one or a heavy one,resulting to big piston/bore clearance.
What seems strange,is the fact that so much attention was put on balancing and main line honing and the most important thing was used as it was,the bores.I mean,a stock or small upgrade power level setup will work ok with that bores,but will need no balancing.If you get balancing means you have lots of revs,lots of torque and the ring/piston blow by is 100% solved.

Regards,

[Thuppu]

I'm sure those bores will be fine to the power limit of the stock pistons, 700-800hp. A bigger piston to wall clearance with the OEM pistons is only a good thing at that level.

[pasbogdan]

Those bores can be 81.19mm Thuppu.We see only the wear marks.So piston to bore clearance could be much more than a good thing

[Thuppu]

Sure they can be, everything is possibly. Factory spec wear limit is 81.09mm. But then again, it's for a stock setup. But you are right, that to be sure, they would need to be measured.

[k.alle]

Well i'll probably not go as far as measure the bores.
The workshop that has carried out this work is very reputable and known to not cut corners.

I just got surprised by those markings and curious to the science behind them.

When I left the block with them I told them to check everything so that it was within spec as the block was an unknown to me.