Piston ring question

[cliffh]

Getting started to put together my full flow 289. I have new pistons and rings from SI. The old pistons have a very thin sort of ring under the second ring from the top. The new rings don't have this. I figure that SI would have provided it if I needed it so my question is more about what is it for and why does the original pistons have it and the new ones don't.

Cliff

[JunkYarDog]

Usually what you are discribing would be a ring from the oil seal ring grove at the bottom of the piston. It could be the old piston had excessive wear in the ring grove and it was a way someone that may of had it apart putting in a new set of rings remedied to much gap. Take a feeler gage and check the grove's on the new and old piston with an old ring and see if the grove on the old piston is wider and if the old ring is thinner.

This is just my guess but that would be my first thought.

[Chipmaker]

It was a common fix to repair a worn ring groove in that manner,back in those days.P.C. and Hastings both made the spacers and the tool to recut the groove.50-60 years ago we did a lot of things that look strange today.Labor was a lot cheeper than parts so we repaired them in place of replacing parts.

[Bud]

The part in question may be a spacer to take up the space in worn ring groves or may have been part of a new ring set if the engine was re-ringed in the past. If you can post a picture, then we can see what you're seeing. I haven't seen any spacers in the ring sets that I've used for engine rebuilds. I would suspect that Ed Reynolds has sent all of the parts that you need for the installation of new pistons. Bud

[Mike Van Veghten]

How thick is this spacer ?

While it could be/most likely is what's noted above, this is also the way Total Seal makes their "Zero Gap" first and second ring..!
They use a full thickness oil control ring though, in a groove in the cast iron ring.

Mike

[cliffh]

Sorry. I wasn't very clear when I said that this extra ring was under the 2nd oil ring. I meant that it was inside of the oil ring not below it. It is a very thin band of spring metal that has several small bends in it and is flat between the bends thus forming a multi-sided circle. This band then presses outward on the inside of the oil ring.
Cliff

[Dan Timberlake]

One piece oil rings (and sometimes the lower compression rings) often have "expanders" like that.
Modern 3 piece oil rings don't.

http://www.grantpistonrings.com/images/art.png

http://d5otzd52uv6zz.cloudfront.net/6973703a-8aa3-46fa-93a3-d12753fe57ac-350.jpg

[cliffh]

Dan. Thanks for the links. I reread my last post carefully and I still messed up. I meant to say compression ring not oil ring. It is the 2nd ring from the top that I am talking about. Apparently, there is some possible advantage to having an "expander" and some (older?) ring sets have them and modern ones don't. Anyway, I think my question is answered.
Thank you,
Cliff

[Bud]

I've seen the expander that you're talking about under compression rings. I would suspect they were used to increase the ring tension on the cylinder walls for better sealing. Modern pistons, rings and cylinder wall finishing have eliminated the need for high tension rings which leads to less drag and longer ring and cylinder life. Bud