piston ring end gap issue ?

[stevieturbo]

Recently took an engine apart. It doesnt have big miles, but definately has an issue here.
Ring gaps were as per instructions, and indeed still are at around 26thou, 97.5mm bore.
Total seal brand

Ive never actually seen a ring that has butted ends, but I'm assuming this has happened ?
Ring has a visible burr at the end of one gap. Ring is also deformed with a raised lip on it's outer circumference. I'm only measuring the raise at about 3thou, but it feels bigger.
Bore markings are at ring gap position.

Was only run at high boost recently, but did have overfuelling issues for a long time before it was tuned recently for more boost.
Ignore any dirt on the rings that is on the photos. The charring/discolouration is on the ring though, and doesnt simply wipe off

This is only on a single piston. Top ring only. ( it also blew a head gasket on this cylinder just before strip down, although that's no big deal. )

[Boosted LS1]

Looks like it wasn't rotating for some reason or other. Was it gapped for turbo use? Detonation could really screw up the figures imo. Oh, if the ends were butting wouldn't they be polished? How would you have a burr if they were butting? Maybe the burr's caused by spread against the cylinder wall.

Edited by Boosted LS1 on Sunday 24th April 21:59

[stevieturbo]

Gapped for blown gas as per instructions.

Engine has never seen any detonation worth mentioning, although briefly was lean at times due to lack of injector.

[Boosted LS1]

But that cylinder blew the head gasket? Something's going on in there. The heat looks like friction. Have you checked the bore's circular?

Edited by Boosted LS1 on Sunday 24th April 22:45

[oakdale]

A lot of heat and pressure damage there, I'd say almost definitely caused by pre ignition (not to be confused with detonation, which is a differnt thing altogether).

Edited by oakdale on Monday 25th April 10:16

[anonymous-user]

On which side of the ring is the lip? (top or bottom side??) Assuming it has been "knocked" there by the lands, what shape are the piston ring gaps in now??? i'm guessing \-/ rather than |-| ;-)

[stevieturbo]

Max_Torque said:

On which side of the ring is the lip? (top or bottom side??) Assuming it has been "knocked" there by the lands, what shape are the piston ring gaps in now??? i'm guessing \-/ rather than |-| ;-)

Not actually sure. There is no top identifier on the ring. Would need to ask the guy who took it apart. I think the lip was to the top side though as evident by the charring marks.

Havent measured or looked at the ring grooves yet, but placing a new ring in them is a snug fit.
Ring ends themselves are as pictured, still square apart from that burr.

[anonymous-user]

I'm having a difficult time thinking how a hard steel ring could have a "lip" formed either by the piston ring land (soft alluminium) without piston damage, or by scuffing up and down the bore (hard iron) but not leaving any trace in/on the bore (bluing/scuffing etc)? Do any of the other pistons top rings have lips?? Do you know if it went in without a lip??

[stevieturbo]

Max_Torque said:

I'm having a difficult time thinking how a hard steel ring could have a "lip" formed either by the piston ring land (soft alluminium) without piston damage, or by scuffing up and down the bore (hard iron) but not leaving any trace in/on the bore (bluing/scuffing etc)? Do any of the other pistons top rings have lips?? Do you know if it went in without a lip??

Rings are not stainless steel.

Absolutely went in with flat rings.

Would need to go back and check the other rings. I didnt get a chance to look at them.
The only marks on the bore are as pictured.

[Pumaracing]

Clearly the ring gap is sufficient for cylinders that aren't overheating so I suggest your only concern is to make sure that the rebuild is done to correct tolerances and that the post build calibration is done properly. The burr on the ring end is not from material from the other gap end. There is no mechanism I can see that would cause that but it may be material deposited from the bore wall that has friction welded into the chamfer gap or it may just be a badly gapped ring from the start.

I wouldn't waste any time worrying about it though. Just fix what you can measure. CR, fueling, sharp edges, valve seating etc.

The honing pattern doesn't appear to have much cross hatch but that may just be the pics.