Piston ring fundamentals

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Yeah, good stuff. Thanks. I have some older stuff from various mfrs but this seems especially well done.
 
That is a great summary...modern engines are so good that I've not done a set of rings in, oh, 30 years now...but the diagrams and explanations in this summary are excellent, even if I never do another set of rings...
 
interesting article. They don't seem to recommend honing the cylinders or a re-ring job. I didn't know that chrome rings were still made, outside of weedeaters and chainsaws. I've seen chrome rings never seat in a rebuild. I am interested in the gapless ring designs. but since i don't hear of them being used in factory engines i wonder if its a cost or reliability issue.
 
Nice read.

Extra credit to who can identify the engine/bay of the vehicle on page 70. It looks visually like a transverse-mounted V-8 engine, but I know of very few of those (outside of previous Cadillac and Lincoln efforts). This doesn't look like a Cadillac or a Lincoln.
 
What a fantastic piece, thank you for sharing!
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Everyone should read this- GREAT illustrations, especially about how sealing of compression and scraping of oil work, and how they can go wrong.
 
Originally Posted By: spasm3
Holden?


The company that made the paper is German, so I was thinking maybe a VW?
 
A good informative piece.

See 1.2.2. and Figure 2.

Many people still do not believe that there is an oil film in the upper cylinder.

It's there, just in very thin films and very low volumes.
 
Can anyone here tell me where the ideas came from that a thicker viscosity oil can actually change the end gap on a piston ring?

Someone in this forum actually dropped that bomb on me and I have searched far and wide for anything to corroborate it...
 
Originally Posted By: SteveSRT8
Can anyone here tell me where the ideas came from that a thicker viscosity oil can actually change the end gap on a piston ring?

Someone in this forum actually dropped that bomb on me and I have searched far and wide for anything to corroborate it...


I've never heard that either. The old rule was .003-004 per inch of bore.
 
Originally Posted By: spasm3
Originally Posted By: SteveSRT8
Can anyone here tell me where the ideas came from that a thicker viscosity oil can actually change the end gap on a piston ring?

Someone in this forum actually dropped that bomb on me and I have searched far and wide for anything to corroborate it...


I've never heard that either. The old rule was .003-004 per inch of bore.


I ran this by a 72 year old Machinist in the Family here and he said balderdash. I also put the question up on some other forums as well. No one anywhere can say it's true.
 
Originally Posted By: SteveSRT8
Can anyone here tell me where the ideas came from that a thicker viscosity oil can actually change the end gap on a piston ring?

Someone in this forum actually dropped that bomb on me and I have searched far and wide for anything to corroborate it...


in full fluid lubrication, there's a layer of fluid between the bore and the ring, reducing the bore size and squeezing the ring gap more closed.

That's all I can think of... the gap will reduce by 6.28312 times the oil film thickness.
 
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