Someone asked me this at work yesterday and I wasnt too sure of the answer.

There are 3 sets of rings on most common pistons, the 2 top rings are the solid thicker rings usually, and then on the bottom there is a small ring, a middle one that looks like a bunch of V's (like VVVV) and then another smaller ring ontop of that. He asked what would happen if you didnt have one of those smaller rings on top of the VVV ring. If it makes sense, what would happen to the worst? No compression in that cylinder, maybe not start, burn a lot of oil? He said it could cause a spun bearing, but I highly doubt it. Not too sure why he asked me this, but I told him I would find out for him. No better place to find out besides here!

Thanks fella's!

-MIKE-

Stroked 2.2L

I don't believe the two smaller rings you are referring to have much to do with compression sealing. The two "thicker" rings are the compression rings. The "/\/\/\/\/\/\/\/\" ring is the oil contol/lubrication ring. From Wikipedia.com:

"...the lower oil control ring is designed to leave a film of lubricating oil a few micrometres thick on the bore, as the piston descends..."

http://en.wikipedia.org/wiki/Piston_ring

Those two smaller rings on either side of the oil control ring "scrape" the oil off the cylinder wall so as it leaves a small film of oil (I think).I think they also secure the oil control ring. I would imagine if one of those were missing than the oil control ring could move about or even become dis-lodged from the ring grove.

From Total Seal Website: http://www.totalseal.com/howdoo.html
Oil Control Rings

Oil control rings are designed along with the piston to effectively permit lubrication of the rings, pistons, wrist pins and cylinder walls without oil migrating into the combustion process. Oil Rings also assist the thermal control of the piston by directing oil into the inside of the piston to help cool the piston dome. Total Seal provides several types of oil rings as may be required including the popular three piece ring consisting of an expander and two rails. The expander provides the tension for the rails and are sold in more than one tension depending on the application. When installing an expander, the expander joint is to be 90 degrees to the wrist pin and the rails should be 1" apart centered on each side of the wrist pin end.

Not sure if this could be related to a spun bearing....maybe if the oil ring got dis-lodged, broke apart and contaminated the oil???

Man....I sure hope this was even close to answering your question....if not forgive my ignorance

he will prolly burn some oil.

If he's got the engine apart far enough to be considering such things, he'd be smart to just get another set of rings now and save many headaches later.

Best case scenario = smoke under load from the exhaust
Worst case scenario = well, think about that oil ring floating around in there.

I may have eyeballed my ring gaps on my first rebuild, but even I saw the importance of making sure I installed all of them.

I am not too sure if he is building a motor or what, he just randomly came up and asked me that.

Thanks for the answers though guys.

-MIKE-

Stroked 2.2L