[outrider02]

Good morning everyone! Trying to sort out some discrepancies I'm seeing on the 2011 US spec M57 I'm rebuilding from my 335d.

First observation, the second piston rings that came off the original pistons look different from the new Hastings rings I've purchased (PN 2D7299). The originals have a chamfered edge on the inside top of the ring, the new ones have a step on the outside bottom of the ring. The package literally says BMW M57 DIESEL 3.0L on it, the other two rings look identical to the originals, so I'm hoping this is just an updated design and not intended for some other M57 variant.

Second issue, the gap on the second ring (both the new and the old) is greater than .45mm, which according to Alldata is the max allowed. I've checked every one of the OE rings, they're all similar.

Is this just bad information in Alldata? Anyone know what the proper ring gap should be?

Thank you!

[outrider02]

Further information, the new second ring is a Napier style ring, the factory one appears to be torsional. This based off pictures I found on Hastings website. I still haven't found any discussion on this or the end gaps.

I've reached out to Hastings directly to ask if it's anything I should be concerned about.

[outrider02]

And a follow-up to my own post again just so the information is out there. Per Hastings, the difference in ring style is no issue on the second compression ring.

I do still have an issue with end gaps being greater than spec. Confirmed in ISTA .40mm is the max recommended value, and both my old and new rings all exceed that. Tested in the freshly honed block and the old one that had spun bearings.

I hate just throwing it together and sending it since I have a lot of money already into gaskets and bearings. But I'm starting to give up hope on finding anyone that has experience going this deep in these engines.

[Tambohamilton]

I see 0.30-0.45 for the second ring end gap for M57T2, same for Top2 (35d)