Educate me on oil control piston rings

[Meirschwartz]

Hello guys. Need some help.
I’m currently rebuilding an M96 water cooled engine.
The block was sleeved with Nikasil cylinders and the displacement was converted from 3.6 to 4.1.
So what am I doing here at the the air cooled engine build area?
The conversion comes with Capricorn pistons and Goetze rings.
The oil control ring is two piece which is something I have never seen before (was expecting the conventional 3 piece). Quick search got me to understand that this type of ring is commonly used in the air cooled engines, and hoping that someone will be kind enough to educate me on how they work.
When installing the ring on the piston, it looks like the ring is too large.
Unlike the first and second compression rings, I cannot compress the oil ring with my fingers to its minimal gap. Is that how it supposed to be?
Any information will be appreciated.
Thanks in advance.
Meir.
Here are pics of what I’m working with.

[porschedude996]

I’ve only seen oil control rings that are three part. The coiled middle piece has a slip joint, where the ends of the wire come together, with a wire on the inside to maintain the arrangement. I don’t see this in your photos. Sorry i’m no help, just giving something you probably already know. Can you get the ring in the cylinder bore? Wrong size ring? I haven’t experienced a mispackaged set of rings. Not that i’ve rebuilt engines in the quantity others here have done.

[gled49]

Fit the oil ring in the cylinder without the expander coil behind it. Check ring gap. Put rings on piston with expander behind oil ring and compression rings as normal. When installing piston with rings in cylinder with ring compressor, oil rings a little and carefully compress rings. The oil ring looks like it’s 2mm, they are a little fragile, be careful.

[Henry Schmidt]

Originally Posted by gled49

Fit the oil ring in the cylinder without the expander coil behind it. Check ring gap. Put rings on piston with expander behind oil ring and compression rings as normal. When installing piston with rings in cylinder with ring compressor, oil rings a little and carefully compress rings. The oil ring looks like it’s 2mm, they are a little fragile, be careful.

All good advise. Remember to index the spring connection opposite the ring gap.

[Meirschwartz]

Originally Posted by gled49

Fit the oil ring in the cylinder without the expander coil behind it. Check ring gap. Put rings on piston with expander behind oil ring and compression rings as normal. When installing piston with rings in cylinder with ring compressor, oil rings a little and carefully compress rings. The oil ring looks like it’s 2mm, they are a little fragile, be careful.

You are correct. the oil ring is 2 mm thick.
I can fit the ring to the bore, measuring about 0.010" gap. Isn’t that too small? (the top compression ring is set to 0.016).
the expender ring will also fit by itself, but not both together.
I installed the expender ring on the piston, and the oil ring on top of it.
the opening of both rings is facing 180 degrees from each other.
if you can notice in the picture, the ring has a dual pitch. I placed the fine pitch facing the opening of the oil ring.
I just want to confirm. it is it normal that I cannot compress both rings by hand when they are installed on the piston?
I assume that once the piston is installed inside the ring compressor tool, the part of the expender ring with the coarse pitch will compress and will conform to the size of the bore.
But this is just an assumption and I do not like to assume. 😊
Another related question about the installation tool as I understand from your comments these rings are fragile. I have both tapered ring compressor:
https://www.amazon.com/gp/product/B07H53N43P/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
and the clamp stile:
https://www.amazon.com/gp/product/B0028QGTP4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
which one will be safer for this application?
Thanks in advance.
Meir.

[Meirschwartz]

Originally Posted by porschedude996

I’ve only seen oil control rings that are three part. The coiled middle piece has a slip joint, where the ends of the wire come together, with a wire on the inside to maintain the arrangement. I don’t see this in your photos. Sorry i’m no help, just giving something you probably already know. Can you get the ring in the cylinder bore? Wrong size ring? I haven’t experienced a mispackaged set of rings. Not that i’ve rebuilt engines in the quantity others here have done.

you are correct. the "spring" is riding on a wire. you cannot see it in the picture as the gap is completely closed. but the wire is inside.

[gled49]

I prefer the ratcheting type as you can move the ring pack around (which is why I oil the rings), while your compressing rings and feel the rings slowly sinking into the groove and not catching on the edge.

[Meirschwartz]

Thanks. I will use that one.
Is it common to have this ring gap smaller than the top ring?
I have a feeling I got rings that are too large.

[RobFrost]

Ask on the porsche engine gurus Facebook group. You'll likely receive an answer from Hartech who are the leading rebuilders of 996 engines.

Sent from my SM-G988B using Tapatalk

[Meirschwartz]

I don’t have a facebook account. I guess it’s about time to get one
Thank yo all.

[Jeff Alton]

For what it is worth, we have CP make us custom pistons with our part number. We use a 3 piece oil control ring on all M96/97 builds.

We see 2 piece ones with aircooled motors.

Cheers

[Meirschwartz]

Originally Posted by Jeff Alton

For what it is worth, we have CP make us custom pistons with our part number. We use a 3 piece oil control ring on all M96/97 builds.

We see 2 piece ones with aircooled motors.

Cheers

Thanks Jeff.
the sleeving process includes custom pistons by Capricorn.
I just needed to gap the ring, and it went on with no issue. just wanted to be sure I'm not damaging anything as this is the first time I came across this type of oil ring.
I'm still curious to know what are the pros and cons of each style.

[stownsen914]

When I had CP make some pistons for an aircooled 3.5L 911, I got a recommendation from CP and one other source to use a 3 piece oil ring with steel (non-chrome) rails. I don't recall the gap specs on the oil ring, but I don't recall needing to adjust it. I did need to gap the top two rings.