1snake

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

Bluestripe67

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

Viet Nam Vett

Well where do you think they are now...?? And what is the chance that they will eventully line up so all the gaps are aligned...?

Can you say "Blow By"

Nowhere Man

then whats making my rings not seat and it burns oil like a ****

Viet Nam Vett

That I can't answer.. Could be a few different things... I'm sure some one with more motor building experience then me will chime in..

Mossy66

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

vettefred

Smilie 388

thats why you hone the cylinder to get a cross hatch
A : to hold a bit of oil on the surface
B: to promote the ring to turn

MasterDave

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

DansYellow66

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.

1snake

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

Avispa

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!!!

kellsdad

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.

wmf62

i always thought the 'crosshatch' honing was for ring seating purposes.
Bill

65specialk

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

Viet Nam Vett

A good friend of mine worked for the "Franklin Mint" as a custom model maker. He did miniture tooling work for the stuff they produced. I gave him a stock set of "427 TurboJet" Emblems from LIC Supply and he did the rest.

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.