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Discussion Starter · #1 ·
How many of you guys have seen the factory recommendations for how to set the positions of the piston ring end gaps? In the shop manual and in the instructions that come with the Stage 3 kit, they tell us to align the top and second compression ring end gaps one-above-the-other! WTF?
I've been building engines for a few decades and have NEVER seen a factory or non-factory publication that says to do such ring alignment. It simply flies in the face of over a hundred years of known IC engine design & development. What could the OEM be thinking?
Granted that any performance lost or oil consumption derived by placing the compression rings in alignment will not likely be great, so long as the end gaps aren't excessive. But combustion pressure pushing the rings outboard will also be effected. Could it be that they want to minimize outboard force at the second combustion ring with this concept?
 

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How many of you guys have seen the factory recommendations for how to set the positions of the piston ring end gaps? In the shop manual and in the instructions that come with the Stage 3 kit, they tell us to align the top and second compression ring end gaps one-above-the-other! WTF?
I've been building engines for a few decades and have NEVER seen a factory or non-factory publication that says to do such ring alignment. It simply flies in the face of over a hundred years of known IC engine design & development. What could the OEM be thinking?
Granted that any performance lost or oil consumption derived by placing the compression rings in alignment will not likely be great, so long as the end gaps aren't excessive. But combustion pressure pushing the rings outboard will also be effected. Could it be that they want to minimize outboard force at the second combustion ring with this concept?
Never heard of that before,hope you find out the reason behind that, maybe crack has made it to spirit lake lol
 

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That is odd. Never seen that before. It's been along time, but I remember most of the my VW engine builds being about 45 degrees away from each other or something like that. It's been 20 years though, lol.

Very Interesting. I look forward to Racinray's take...
 

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I also was always taught that, as a general rule, you never align the ring gaps to each other. On the other hand, I've also always been told that when a factory spec is in conflict with a "rule of thumb" you are to follow the factory spec. Rules of thumb are fine in the absence of conflicting information, but if the engineers take the time to specify a deviation from that rule, then you should follow it. We don't always get the reasoning behind it, and the engineers often don't feel the need to supply a reason, but you can bet that there is one.

Here's a little bit of history to illustrated the point. This story was relayed to me as a young man working on the B1-B program to illustrate this very point. Not widely known public knowledge but also not "classified" Many folks know who Chuck Yeager is (those who don't need to look him up). While North American Aircraft was developing the YF-100 (later became operational as the F-100A) there were a mysterious series of crashes that killed pilots. These crashes seemed to always follow rolls to inverted flight, as the pilots applied power to pull out they would lose control and crash. Yeager took one up and went inverted at a very high altitude to allow him reaction time. He found that when power was applied the elevator controls locked up. He found that if he did a counter-intuitive maneuver and pulled power all the way back control authority was returned and he was able to land safely. Consequent inspection of the elevator controls revealed the cause of the failure. A bolt that connected the elevator assembly to the pivot shaft in the horizontal stabilizer assembly had been installed "upside down" by the assembly line mechanic. (Rule of thumb on bolt installation is to install bolts in vertical holes from the top, so that if the nut comes off the bolt can't fall out. These bolts were installed this way, despite being specified in the blueprints as being installed head down.) When the G-force was reversed on the structure the protruding tail of the bolt dropped and contacted a structural member and locked it up. They inspected all of the aircraft already built, and discovered that they all were the same. They then went to the assembly line and found the mechanic that had done it. They asked him why and he told them "the print was wrong". They informed him simply that he needed to install the bolts as designed. They did not write him up and did not tell him what the results of his mistake had been in order to spare him the guilt. No one who knew the story repeated it at all until after this man died, and when they did finally tell it as a useful parable, his name was never mentioned in order to spare his family also.

The story was related to me and our crew by one of the engineers that had been involved in the deal, and what brought it out was a spec on the B1-B nacelle that was not to "rule of thumb." They were calling hole sizes for hi-loc and huck fasteners "too large" for the fasteners. (Example: 3/16 fastener "normally" requires a hold diameter of .187", and the prints for the nacelle specified .191" nominal. This made a loose fit on the fastener and made them difficult to install as they wiggled around in the hole. We requested clarification on the matter and were told that the prints were right, the holes had to be that size in order to allow the necessary flex for proper operation of the assembly during flight. If the holes were drilled "the right size" there would be no required flexibility, and many fasteners would shear off or damage the structure .

Bottom line, maybe there's a reason for installing the rings this way, but we don't know what it is. We do know that this has been discussed here a few years ago, and that Polaris is aware of it but there has been no clarification or change in the spec.
 

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I also was always taught that, as a general rule, you never align the ring gaps to each other. On the other hand, I've also always been told that when a factory spec is in conflict with a "rule of thumb" you are to follow the factory spec. Rules of thumb are fine in the absence of conflicting information, but if the engineers take the time to specify a deviation from that rule, then you should follow it. We don't always get the reasoning behind it, and the engineers often don't feel the need to supply a reason, but you can bet that there is one.

Here's a little bit of history to illustrated the point. This story was relayed to me as a young man working on the B1-B program to illustrate this very point. Not widely known public knowledge but also not "classified" Many folks know who Chuck Yeager is (those who don't need to look him up). While North American Aircraft was developing the YF-100 (later became operational as the F-100A) there were a mysterious series of crashes that killed pilots. These crashes seemed to always follow rolls to inverted flight, as the pilots applied power to pull out they would lose control and crash. Yeager took one up and went inverted at a very high altitude to allow him reaction time. He found that when power was applied the elevator controls locked up. He found that if he did a counter-intuitive maneuver and pulled power all the way back control authority was returned and he was able to land safely. Consequent inspection of the elevator controls revealed the cause of the failure. A bolt that connected the elevator assembly to the pivot shaft in the horizontal stabilizer assembly had been installed "upside down" by the assembly line mechanic. (Rule of thumb on bolt installation is to install bolts in vertical holes from the top, so that if the nut comes off the bolt can't fall out. These bolts were installed this way, despite being specified in the blueprints as being installed head down.) When the G-force was reversed on the structure the protruding tail of the bolt dropped and contacted a structural member and locked it up. They inspected all of the aircraft already built, and discovered that they all were the same. They then went to the assembly line and found the mechanic that had done it. They asked him why and he told them "the print was wrong". They informed him simply that he needed to install the bolts as designed. They did not write him up and did not tell him what the results of his mistake had been in order to spare him the guilt. No one who knew the story repeated it at all until after this man died, and when they did finally tell it as a useful parable, his name was never mentioned in order to spare his family also.

The story was related to me and our crew by one of the engineers that had been involved in the deal, and what brought it out was a spec on the B1-B nacelle that was not to "rule of thumb." They were calling hole sizes for hi-loc and huck fasteners "too large" for the fasteners. (Example: 3/13 fastener "normally" requires a hold diameter of .187", and the prints for the nacelle specified .191" nominal. This made a loose fit on the fastener and made them difficult to install as they wiggled around in the hole. We requested clarification on the matter and were told that the prints were right, the holes had to be that size in order to allow the necessary flex for proper operation of the assembly during flight. If the holes were drilled "the right size" there would be no required flexibility, and many fasteners would shear off or damage the structure .

Bottom line, maybe there's a reason for installing the rings this way, but we don't know what it is. We do know that this has been discussed here a few years ago, and that Polaris is aware of it but there has been no clarification or change in the spec.
There should be some clarification from the engineers, just to make sure that manual wasn't a typo mistake.
 

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There should be some clarification from the engineers, just to make sure that manual wasn't a typo mistake.
Well, I don't disagree, there SHOULD be. I was just sharing info is all. I'd absolutely like to know for sure that it is correct, and why. That said, if the manual has not been updated in 5 years, when we know that the issue has been brought to Polaris' attention, well then..........
 

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It is an old wives tail to NOT have end gaps near each other.

FIRST OF ALL....there is ONLY ONE compression ring, the top ring. The second ring has virtually no affect as a compression ring, and it's sole job is as an oil scraper. It's function is to scrape oil off the cylinder wall on the piston's down stroke so the bottom ring, the oil control ring can channel the oil back into the sump. Typically there are 2 common designs for that purpose. One design is a chamfer on the bottom outer edge of the second ring, Another design is a 2 degree taper on the second ring, which does the same scraping job. When that 2 degree taper is worn flat, oil consumption goes up.

I believe it was Shardy discovered why Indian has the rings staggered by accident. In his top end work on his skoot he neglected to align the rings as per specs, and one cylinder burned lotsa oil. The improper positioning of the oil ring rails allowed oil to get into the combustion chamber.

I re-rung my Busa twice after I installed the big bore kit. The Nikasil coating Millennium used back then was extremely hard on that second ring, and in about 30,000 miles it was burning oil, and there was NO taper left on the second ring. I do have an established ring position procedure I follow, and one thing I saw when the engine was torn down for re-ringing was the rings were NOT in the same position in their grooves as when the engine was built. That Nikasil coating was so hard honing was not necessary, and new rings seated in quickly!

I bored/sleeved/decked/honed/o-ringed cylinders for 10 years, doing over 5000 jobs on all types of cylinders and pistons. I learned alot then.

RACNRAY
 

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Discussion Starter · #9 ·
Good info RACNRAY and I agree with your points regarding how piston rings operate, but it doesn't appear to clarify your position on whether or not the end gaps of the top two rings should be aligned, as the OEM indicates. And I agree with the other guys who presume that Indian MUST have a reason for telling us that the top two end gaps should be aligned, even though they apparently don't feel that we have a need to know that reason.
Still, for what it's worth, you can call me a rebel, but I built my Stage 3 Roadmaster with the end gaps fully staggered, as per convention that goes back a lot further than my few decades of engine building. And until I hear a plausible explanation for Indian's end gap positioning, I ain't gonna do it.
 

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The positioning of the end gaps for the top and second ring is irrelevant, what shardy found was the positioning of the oil ring rails something to do with oil channels in the piston and that was the reason for his oil consumption. On any engine at some point in time the gaps on the top and second ring will align , nothing can be done about that but the reality is there is no blow by when they do a align.
RACNRAY
 

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I read that in the service manual too and it made me scratch my head. I’m definitely curious how your results will be by not following the Indian instructions. I’m guessing that the factory installs the 111 rings as per the manual. So maybe it doesn’t matter?
 

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So Our Gapless rings were a waste of money on the DragBike?????
Maybe, But the Times Improved... so... I'll keep my impressions of how Rings work...
 

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So Our Gapless rings were a waste of money on the DragBike?????
Maybe, But the Times Improved... so... I'll keep my impressions of how Rings work...
I gas ported the pistons on my drag bike so there was no need for gapless 2nd rings. The engine was torn down every 75 passes or so to re-ring and check the head. 1327cc, 18-1 compression ratio AND about 350 pnds cranking compression (I had to buy a diesel engine compression gauge)!!

I dn't see a concern about the top and second ring alignment as they will "un align" over miles, but as Shardy found out it was the positioning of the expander and oil ring rails that really what is important on these pistons.

RACNRAY
 

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Do they say what ring end gap they want.they run these engines hot,I would imagine a .0050 end gap.
TOP is .006" minimum, 2nd is .013" minimum, rails are .006" minimum.

RACNRAY
 

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I just go with j and p.those rings are usually between 15 and 19.in they go.you really don't want to line up gaps like that.
 
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