Topic: Which piston ring is which?

[JBMorse]

I am installing some new piston rings that I purchased on EBay a few years ago, and can't decide what the order is. I thought the ring with the shiny edge is the top ring, and the flat black ring the middle or "oil scraper." However, I also remember reading somewhere that ring manufacturers typically package rings in the exact order they should be installed.
These were packaged with the shiny ring in the middle and the black one on top. So which is it? Do they go on the piston in this order? I'm confused...
Thanks!

[70CB750]

Yes, shiny edge is the top ring


Here:

http://forums.sohc4.net/index.php?topic=64519.0

[70CB750]

Except do not bother lining up gaps, rings in 4 stroke engine rotate.

[70CB750]

Some reading:

[JBMorse]

Thanks! I don't know if I'm remembering wrong about the way the package piston rings, or if this company doesn't have good attention to detail! Either way I appreciate the clarity.

[Phinn]

The markings on the tips of the rings (near the gaps) point upward.  Some rings don't have markings, though.

[That 70s Bike]

I've done it this way on the limited times I've installed pistons. Is it the case that they may move over time and have been found un-staggered later?

[FunJimmy]

Except do not bother lining up gaps, rings in 4 stroke engine rotate.

I've heard this type of comment before and don't understand the origins of the logic.
How is it possible for the rings to rotate in a high pressure linear application?
The cylinders don't mechanics like rifling to facilitate rotational movement of the rings.
How is it possible?

[70CB750]

I dont know why they rotate, but there are studies proving it:

http://kns.org/jknsfile/v31/A04803285773.pdf

Did you ever work on 2 stroke engine?  2 strokes have pins to keep ring from rotating, if the ring did not have tendency to rotate, no pin would be needed.

[FunJimmy]

I dont know why they rotate, but there are studies proving it:

Did you ever work on 2 stroke engine?  2 strokes have pins to keep ring from rotating, if the ring did not have tendency to rotate, no pin would be needed.

Ya I know 2 stroke rings are pinned and I've read a few articles that suggest cylinder cross hatch generates rotation but that wears off pretty fast. I would think the cylinder pressure would force the rings tight to the landings preventing rotation. Boggles the mind.

Thanks for the technical paper. I'm looking forward to reading it.

[jonda500]

Except do not bother lining up gaps, rings in 4 stroke engine rotate.

Just make sure the gaps initially aren't all lined up, any mechanic in the world will tell you to stagger the gaps 120 degrees!
John

[Don R]

 While in the long run spacing the gaps may (or may not) matter, it certainly doesn't hurt anything and it takes mere seconds.

[70CB750]

While in the long run spacing the gaps may (or may not) matter, it certainly doesn't hurt anything and it takes mere seconds.

Haha, that's what i did when building Red's engine.  But I will be pulling the engine this fall to replace cam chain tensioner and I am really curious how the rings are oriented.

[70CB750]

Also here is an interesting article on ring gaps:

http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php

Quote:

... the size of the ring gap.  Yes, there is a minimum but this varies considerably depending on the material used.  Normally 0.003"/0.004" per inch of bore size is given but where, for example, low expansion SG (spheroidal graphite) iron is used, it can be considerably less. 

 It’s no problem if the gap is too small because it can, in the final analysis, be filed bigger but what do you do if it's too big?  You cannot stick a bit extra in there!   

Well, the answer to that was that you melted them down and started afresh – until AE research asked the question, "What is too big?" and set out to quantify that.  The results were interesting – very interesting – and what you are about to read was kept quiet because it bestowed an enormous commercial advantage on AE.  This is probably the first time the information has been published although the research was undertaken in the late 1970's – almost 25 years ago.

A Ford Kent engine was stripped and fitted with compression rings which had end gaps of 0.015" when fitted in the bores.  The engine was wired up with the usual telemetry to measure blow-by and oil consumption and then run in one of the test cells.  After making due note of the blow-by and oil consumption, the engine was stripped and fitted with new compression rings with gaps of 0.025" and the test cycle repeated. 

These rings were subsequently replaced by ones having end gaps of 0.035" and the test cycle repeated again.  It had been planned to stop at 0.035" gaps ---------->       but the results were so interesting that it was agreed to proceed to 0.045” and then not to 0.0055” but to 0.0625”  – 1/16"!   

Whoever heard of rings with 1/16” gaps – a ridiculous figure – but the interesting thing was that the increase in blow-by and oil consumption at 0.0625” was only marginally above the figures obtained with 0.015” gaps.

[That 70s Bike]

I have a 4 pack of those same "hy" rings also from a few years back and not installed yet.

[MRieck]

I have noticed a trend of increasing end gap over the past 10 years. .003 was the standard for ever....now it is .004 or .005. Nitrous, turbo's etc have much larger #'s