Piston ring orientation

[Boiler Ben]

I have my cam and crank installed and am ready to reinstall pistons.  Is there a particular way to clock the ring gaps when installing the pistons in the block?  I haven’t found anything that discusses this.

[cjshaker]

The short answer is no, just make sure they're staggered and not lined up.
In practice, I avoid putting them on thrust sides, but in reality, they're going to move.

[Rory428]

I have never had a set of pistons or rings that did not specify how the manufactures suggested the rings be positioned for assembly. If not, for some reason, the information should be easy to find in service manuals, piston and ring catalogs or manuals, or any numbers of engine books. Not every manufacturer specifies the same ring orientation, or ring gap requirements, assembly lubrication recommendations, or clearances, so always best to use the suggestions of the manufacturer.

[Dyno]

Stagger them around as previously mentioned. As long as gaps are not lined up.

[Barry_R]

The short answer is no, just make sure they're staggered and not lined up.
In practice, I avoid putting them on thrust sides, but in reality, they're going to move.

Accurate info

[Boiler Ben]

Thank you.  Will proceed.

[jayb]

Interesting, I've been installing piston rings the same way for 40 years, following the info from JE pistons.  They specify the top ring and the second ring gaps 180 degrees from each other, and on the non-thrust sides.  The also specify oil ring orientation.  We all know that the rings will rotate once the engine is running, so not sure how much difference any of this makes...

https://www.jepistons.com/ring-installation-guide-4032-pistons-instructions/?srsltid=AfmBOorSZvcqznc4a23SUkYuPa7-V3lFJzC89jNVS7k7oEvO89ILD8B-

[GerryP]

It made more sense more than 30 years ago, Jay.  We didn't know better and nobody asked why?  The theory was the cylinder pressure and combustion gasses with staggered rings would have a hard time making a turn from one piston ring gap to another.  Maybe in only the slightest degree.  Then someone dynamically tested the theory and proved the rings rotate independently the full circumference of the piston at a pretty good clip.  If the rings stayed in the same place or orientation, then 2 stroke rings wouldn't need to be pinned.  We have the conflicting theory too that warns against a stuck ring digging a vertical groove in the cylinder wall...something that doesn't happen with pinned 2 stroke rings.  I guess do it if it gives one a sense of security by "doing it the right way".

[e philpott]

Two stroke engines can't risk ring rotation because the ring end will pop into the lower intake ports or upper exhaust port and lock the engine up or cause major damage to the engine

[GerryP]

Two stroke engines can't risk ring rotation because the ring end will pop into the lower intake ports or upper exhaust port and lock the engine up or cause major damage to the engine

I know that.  That is why the rings are pinned.

[Barry_R]

It made more sense more than 30 years ago, Jay.  We didn't know better and nobody asked why?  The theory was the cylinder pressure and combustion gasses with staggered rings would have a hard time making a turn from one piston ring gap to another.  Maybe in only the slightest degree.  Then someone dynamically tested the theory and proved the rings rotate independently the full circumference of the piston at a pretty good clip.  If the rings stayed in the same place or orientation, then 2 stroke rings wouldn't need to be pinned.  We have the conflicting theory too that warns against a stuck ring digging a vertical groove in the cylinder wall...something that doesn't happen with pinned 2 stroke rings.  I guess do it if it gives one a sense of security by "doing it the right way".

They don't move all that fast.  But they do rotate.
Somebody at Sealed Power tested this back in the proverbial "day".  I think they used a radioactive pellet embedded in the ring. 
I recall the answer being around 10-12 RPM.
An improper bore finish can get them really spinning fast - which will show up as dramatic ring and piston wear.