Learn something new every day
Thread Starter
Le Mans Master
Joined: Dec 2007
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From: Puget Sound
Learn something new every day
While cruisin' through another forum, I found an interesting thread about piston rings. I did not know that the rings actually rotate on the piston while running. There were a lot of posts substantiating this. This is from a post by a MAJOR engine builder - if you do some SAE research, you'll find that they can rotate up to around 10 rpms depending on several variables. Sometimes they can rotate at 1 rpm or slower.
I always thought they stayed put. That's why you staggered the ring gaps upon assembly and that ring groove wear was from the up & down forces, not the the ring spinning in the groove.
I guess you learn something new every day.
Jim
I always thought they stayed put. That's why you staggered the ring gaps upon assembly and that ring groove wear was from the up & down forces, not the the ring spinning in the groove.
I guess you learn something new every day.
Jim
Race Director
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C2 of the Year Finalist - Modified 2020
Jim,
That's interesting, never knew of it or gave it any thought. I remember when I built my motor in '84 I paid close attention to staggering the rings.
Dennis
That's interesting, never knew of it or gave it any thought. I remember when I built my motor in '84 I paid close attention to staggering the rings.
Dennis
Le Mans Master
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And what is the chance that they will eventully line up so all the gaps are aligned...?Can you say "Blow By"
Team Owner
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From: Sitting in his Nowhere land Hanover Pa
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Le Mans Master
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From: Egg Harbor Township NJ
2015 C2 of Year
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Drifting
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From: Lake Villa Illinois
St. Jude Donor '14
I'd have to see it to believe it. What would be the driving force pushing the rings round and round? 
I've never seen any spiral wear marks in a cylinder, but I am certainly no expert.
Gerry
I've never seen any spiral wear marks in a cylinder, but I am certainly no expert.
Gerry
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From: Dove Mountain Arizona
Interesting.....I do know that on two cycle engines there are dowels in the piston ring grooves to keep the ring ends from moving into the intake and exhaust openings and breaking. Did not know that the rings on a four stroke engine rotated. :o
Race Director
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From: Central Arkansas
Yeah - I posted that. Someone commented in a thread here that piston rings circulate on pistons and I kind of had one of those WKRP in Cincinati, Turkey drop episode moments - "As God is my witness, I thought Turkeys could fly." I don't know how I've been around all these years and didn't know rings were intended to spin on pistons. But now I know.
It would have been a lot simpler and less embarrasing if I had simply Googled "piston ring rotation" first.
Now if I can figure out why they rotate - I don't quite buy the cross hatch honing theory.
It would have been a lot simpler and less embarrasing if I had simply Googled "piston ring rotation" first.
Now if I can figure out why they rotate - I don't quite buy the cross hatch honing theory.
Thread Starter
Le Mans Master
Joined: Dec 2007
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From: Puget Sound
I didn't add the part about 2 cycle rings being pinned to prevent rotation because I didn't want to confuse everyone but, yes, they are. 4 cycle motors are not.
I've built many motors and have always staggered the ring gaps like the manufacturer stated to do. In hindsight, I've torn apart many original motors and always wondered why the ring gaps varied so much and were no way close to how they should have been assembled . Now I know.
Jim
Last edited by 1snake; Dec 8, 2010 at 09:39 PM.
Safety Car
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From: Corpus Christi, TX
Total Seal or Childs & Albert gapless piston rings. Then it doesn't matter which way they're rotationally oriented. Get the block stress plate honed and never suffer blow by again. The red thing's 427 pulls 2 inches of vacuum through the crankcase intake vent at idle. No smoke, no fuss, no compression variation between cylinders. End of story.
Viet Nam Vett - where'd ya get those 502 embems? Too cool!!!
Viet Nam Vett - where'd ya get those 502 embems? Too cool!!!
Melting Slicks
Joined: May 2001
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From: Dadeville AL
The most popular explanation for ring rotation on the other web site was coriolis forces like for the water draining from the toilet. That's why the rings in cars at the equator don't spin at all. 
Just kidding.
Just kidding.
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From: Inverness FL
St. Jude Donor '07
Burning Brakes
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From: Gasburg Virginia
Not a Corvette but had a guy called me with a problem after he rebuilt his engine. Oil was pumping out of the intake!! Had new pistons and rings? He had installed the rings upside down and instead of making compression it was an oil pump. Some rings are tapered. I turned them over and it now has 100K miles on it with no problems. Dave
Last edited by 65specialk; Dec 9, 2010 at 09:12 AM. Reason: spelling
Le Mans Master
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From: Egg Harbor Township NJ
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Total Seal or Childs & Albert gapless piston rings. Then it doesn't matter which way they're rotationally oriented. Get the block stress plate honed and never suffer blow by again. The red thing's 427 pulls 2 inches of vacuum through the crankcase intake vent at idle. No smoke, no fuss, no compression variation between cylinders. End of story.
Viet Nam Vett - where'd ya get those 502 embems? Too cool!!!
Viet Nam Vett - where'd ya get those 502 embems? Too cool!!!
Viet Nam Vett - where'd ya get those 502 embems? Too cool!!
He milled out the 427 down to the level part of the emblem ...then custom made the 502 numbers to match the script from the 502 Valve covers.....then painted the emblem black in the seating area and epoxied them in. Took him a while to do them for me... He said he'd never do that again...siad it was a Big PITA.