Putting together a 383 chevy motor. I have always struggled with this subject. I have a couple of diagrams. All of them show basically the same pattern and it appears that they are telling you to put the 1st compression ring perpendicular to the wrist pin and second compression 180 degrees from that and then the oil rings and separator in another pattern. My conundrum is that the one diagram does not say to rotate the pattern from bank to bank. It references the front of the engine and left and right side. My interpretation of the diagram is that I would set the pattern in the same orientation looking at the top of the engine. So, I would have 1st compression on the thrust side of the piston on the passenger side of the motor, and the 1st compression on the non-thrust side of the piston on the driver side. This has never made sense to me and I believe I have always modified it to put 1st compression gap on the non-thrust side on both banks and just follow the pattern from there. Any definitive knowledge out there? I have searched the internet for 2 days, including several piston and ring manufacturer sites with no good info and no definitive answers. Thanks in advance, Dan
I used to know someone that did extensive testing on this. Even after only a few seconds on running the rings had spun to different locations upon teardown. From what I understand the pattern you describe is only for those first few seconds of running to assure compression.
How would a ring spin on the piston? There are no forces to twist them. Every engine I've assembled and taken apart again has the rings in the position I set them. I like to put the compression ring gaps about 10 degrees from the wrist pin ends on opposite sides of the piston and oil ring end gaps 10 degrees on the other side. I doubt that it really matters as long as you don't line all of the gaps up.
Vibration moves them. I have rarely seen them where I put them, on tear down. Often just a little movement, but occasionally near 180º out.
As you can see, some people believe it and some don't. In either case it doesn't hurt to clock the gaps of compression rings away from each other, but I think a complex pattern from bank to bank is just plain overkill.
If you set it up to give any leakage through the ring gap the longest possible distance to travel (i.e. 180 degrees out from the previous one), that's the bast you can do. They will spin with vibration.
Bore finish affects ring rotation according to Hastings http://www.hastingsmfg.com/Master_Catalog_Pdfs/Master2012.pdf
I put the comp rings 180 deg apart and not lined up with the wrist pin axis. The oil ring gap can go pretty much anywhere except lined up with one of the other gaps.
I had not ever heard of that term, but was just taught by some real good mechanics to just make sure they are staggered.
My time with Uncle Sam and the M16 taught me that no matter how you stagger the rings they will end up in a totally different place! Posted using the Full Custom H.A.M.B. App!
I was taught the top ring to the opposite side of the notch in the top of the piston,second in line with the notch oil expander opposite the notch,and the top and bottom rail about an inch away, one in one direction of the expander opening, the other the opposite direction. Has always worked for me.,
I've always stggered them about 90 degrees, at more or less the 9 oclock and 3 o clock positions. Never paid any attention afterwards, never had a problem,
Had a technical rep from Perfect Circle Piston Rings talk to our high school vocational auto mechanics class in 1967. "Put the rings in any position you want to when you assemble it. Run it for a little while and if the rings are still in the same position as they started out, I'll buy your lunch".
That's about it. But like a lot of things, it can get over thought. *sigh* When does spring get here?
Best to follow the installation instructions from the piston ring mfg'er. Man, who can think with your avatar showing?
good point Blowby, if the rings don't rotate why do the 2 cycle motors have pins to keep them from rotating?
My welding class couldn't. I shared her video at last nights class. Even the young bucks were in awe.
Rings rotate, you dont ever want to see a 2 smoke ring rotate. The carnage created when that ring end gets caught on a port can be quiet extensive/expensive.
^^^ tfeverfred, that's awesome! Hey if anyone gets so hung up over ring gap clocking, just buy a Total Seal Gapless ring set and stop worrying
yep and you want to make sure they are checked for gap several times , 8000 rpm makes alot of swarf in a cylinder I know that for a fact ... glad the liners were replacable ( but brother who was lazy wasn't ) .. the honing grooves is what moves them around is what we were taught by the TRW tech guys , and it shouldn't matter once its fired and they seat as the gap will close down in a matter of a few minutes from the heat , but when we set them it was 180 apart and never inline with the wrist pin and the oil rings were 90 apart and away from the lower ring gap ..
The guy I'm referring to went to a trade school. They actually put engines together, ran them and tore them apart just to see if the rings turned. He said no matter how long or short of time they ran the rings would be in different locations. I have no reason not to believe him.
If rings rotate on the piston, they would quickly wear the ring lands out in an aluminum piston. Detroit Diesel 2 cycle engines didn't have anything on the piston to prevent rotation. The sleeves have ports all of the way around and the ends of the rings don't catch on them.
the ports on a 2 stroke Detroit are close enough together it's not a problem but in a dirt bike engine the port is fairly large and could catch a edge if a ring moved there there would not be enough tension to keep the end in the land
Rings rotate !!!! Period!! So says Sealed Power for one. If they did not they would end up sticking in the grooves [see what happends in 2 stroke engines over time where they are pinned].
I have probably built hundreds of engines over the years and torn down 3 times as many...I highly doubt the rings stay where you put them when you install them. As long as they're installed correctly on the piston (correct groove and right side up, etc) I really don't think it matters much how you orient them - so long as the gaps are staggered. The only bit of advice I can offer is to always do it the same way - every time. For me - if the piston has a notch on the top indicating 'front', I always put the top ring gap 180* from that notch and then stagger the rest 180* from that - including the oil ring(s). Been doing it that way for 25 years and never had a problem.
"The rings have a natural tendency to turn in the groove when the piston changes direction at the top and bottom of the stroke, and they must be allowed to turn freely. This action cleans carbon out of the top groove and leaves the compression ring free to expand as combustion pressure enters the groove." Power Secrets, Smokey Yunick, chapter 3.
All the (small) 2-strokes that I ever worked on had pinned rings. In other words, there was a pin in the ring land on the piston and a corresponding notch at the ring end gap. When installed, the gap is positioned by the pin so that the ring cannot rotate. If not, then the ends would surely snag on the edge of an intake or exhaust port and cause problems.
True - however those engines have huge bores with 'significant' piston rings that hold their shape very well - plus the ports are slightly chamfered on their edges.
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