Is ring gap orientation really that critical ?

[ertech]

Is ring gap orientation really that critical ?
When I assembled my engine I had a hard time putting 2 pistons trough the rings might have turned.
Also would i have symptoms if I broke a ring?
Thanks
Erick

[Flat6pac]

The rings will orientate themselves to where they want to run almost immediately on start up
Bruce

[Amstaff]

I always put them opposite of each other. I assume they will turn some as the motor is run.

Excessive oil consumption and loss of compression are a couple of issues resulting from broken rings.

[HawgRyder]

Rings rotate around the piston under normal conditions.
If they stayed put...then 2 stokes would not have to be pinned to prevent this.
On a 2 stroke piston...there are small pins in the ring lands...and the rings have little cutouts on the gap ends to fit over or around these pins.
Personally...I like to start with the compression rings about 120deg apart...with the gaps just below the piston pin ends...and the oil ring with its gap (if it's a one piece) the the top of the piston (so the oil doesn't have an easy time getting out).
Bob

[Gordo2]

A bit late for your project... however, I found this tool most helpful installing the pistons:

Wiseco Tapered Piston Ring Compressor Review

Good luck,

Gordo

[porschetub]

Originally Posted by HawgRyder

Rings rotate around the piston under normal conditions.
If they stayed put...then 2 stokes would not have to be pinned to prevent this.
On a 2 stroke piston...there are small pins in the ring lands...and the rings have little cutouts on the gap ends to fit over or around these pins.
Personally...I like to start with the compression rings about 120deg apart...with the gaps just below the piston pin ends...and the oil ring with its gap (if it's a one piece) the the top of the piston (so the oil doesn't have an easy time getting out).
Bob

spaced one third around is good as Bob says, a very large diesel 2 stroke (4500 hp) I saw spun a ring after the one the ring index pins fell out and all was fine until the ring turned and went out the transfer port thru the blower and then the turbo,110K later the motor was fixed ????
Yep they do move in the bore so said spacing is important. but the accuracy of the spacing isn't absolutely critical,close is good enough.

[E Sully]

Gap location and pinning is important in a 2 stroke due to the intake and transfer ports cut into the cylinder walls, don't want the ring ends getting caught in the ports as they pass by. It never hurts to stagger the gaps so they don't all line up on initial install, but 4 strokes rings will rotate.

[304065]

Maestro's Library | The Maestro's Porsche 356 & Porsche 912 Problem-Solving Site

[JFairman]

The factory manual has a diagram showing where the ring gaps should be. For what it's worth it says from the top compression working down they should be positioned at clock positions 4, 10, and 2.



I've posted this diagram before and the subject has come up again so I hope this helps.

I installed my new Mahle 3.3 pistons and cylinders 5 months ago with the ring gaps positioned this way and it's running perfect. Runs smooth and strong and the exhaust never smokes. This is in a 1987 911 turbo.
When I took the pistons out of the cylinders that were in the car the ring gaps were real close to this position.

[DSPTurtle]

I can't remember if it was the 2.7 or 3.2 boxster motor I just put together, but it also has the described pins. Made it pretty darn easy to locate those little rings. Getting the pistons in the bore is a different story.
For the OP, I like to see where the rings are sitting when I pull them apart. Almost never where you would expect, but I have noticed that the oil scraper ring does in fact come out most time with its gap in the 12 o'clock position. So that is always the one I stress about the most. As long as none of the rings are exactly aligned with each other, you should be fine.

[JFairman]

I installed the pistons into the cylinders before installing them into the motor.
Pushing down with my thumbs the pistons pressed into the bottom of the cylinders smooth and easy while the cylinders were top side down on a workbench.
I had them snugged inside a wide Sears spring steel type piston ring compressor with oil on the rings and redline assembly lube smeared on the piston skirts.

Here's a few pics while installing them into the motor.
I did it in my driveway with the motor in the car while the back of the car was up on jack stands and the back of the motor lowered down onto a jack stand. I don't have a motor stand and my back wasn't sore that week so this worked out fine for me.
I had the pieces of aluminum foil there to keep a wristpin circlip from possibly flying into the case if one got away from me while installing it. The mahle circlips are thinner than JE circlips and easy to install though so that didn't happen.

The blue stuff is hylomar.
I have a little more on there than necessary but I didn't want to chance oil leaks and any that squeezed out while tightening down the head stud nuts wiped off easily with a rag soaked with wash lacquer thinner.
I used hondabond on the cam towers and they don't leak either.

[Edelweiss]

Dear Sirs,

wrote this in an other thread - think it will fit here too:

Dear Sirs,

doing min. one engine a week here is first hand information:

For sure it is so right as essential to be very correct and exact about the mounting position of the piston rings.

Why bother is a shocking statement to my ears.

And yes it is right - depending on the ring and cylinder material the rings are moving a little - some few degrees - during the break in process.

The physics behind this phenomena is simple - the rings are building sort of a labyrinth seal and the gases are traveling through it causing lateral forces to the rings ends in the gap zone.

This is without any effect as the rings are " broken in " to the cylinder surface, from that moment on the rings are not changing position any more and stay where they are for the engines lifespan.

We service our race engines on a yearly basis and when the cylinders come off I see the piston rings, more or less, exactly where they where positioned during the mounting process.

At some application we use gap less rings from total seal with good result - using this top rings is minimising the ring rotation against zero.

There is I a logic inside all this - the braking in means the rings found their position to the cylinder and the sealing effect against gas pressure from head side and oil from the crank side gets to its maximum. If they where not stop moving they would never break in, never seal and as an effect would wear out quick.

We produce our own nikasil plated cylinders in our own casting and we are using Mahle 124 to produce our pistons ( not even Mahle is using this high end material any more by the way ) so we deliver this parts to all top european engine builders and have to answer questions around this all day.

When braking in - use special break in oil or simple mineralic 10/40, never start a new engine using synth. oil with high viscosity.

If it is not a race engine and you have the time go for it approx 5000 km before you change for the premium synthetic juice.

We use nothing but Motul 20W60 then - this is by far the best for air cooled engines from our daily experience.

Best reg.

Dirk

https://www.facebook.com/edelweissmotorsport

[wndsnd]

Originally Posted by JFairman

I installed the pistons into the cylinders before installing them into the motor.
Pushing down with my thumbs the pistons pressed into the bottom of the cylinders smooth and easy while the cylinders were top side down on a workbench.
I had them snugged inside a wide Sears spring steel type piston ring compressor with oil on the rings and redline assembly lube smeared on the piston skirts.

Here's a few pics while installing them into the motor.
I did it in my driveway with the motor in the car while the back of the car was up on jack stands and the back of the motor lowered down onto a jack stand. I don't have a motor stand and my back wasn't sore that week so this worked out fine for me.
I had the pieces of aluminum foil there to keep a wristpin circlip from possibly flying into the case if one got away from me while installing it. The mahle circlips are thinner than JE circlips and easy to install though so that didn't happen.

The blue stuff is hylomar.
I have a little more on there than necessary but I didn't want to chance oil leaks and any that squeezed out while tightening down the head stud nuts wiped off easily with a rag soaked with wash lacquer thinner.
I used hondabond on the cam towers and they don't leak either.

What head studs are these?

Tks
John

[JFairman]

They're ARP headstuds. I put them in with red loctite.
They're not bottomed out in the case threads, the top thread is 135mm from the case.