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Dave WM

ring gap posistion

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Posted (edited)

I tried searching and reading the FSM and the rebuild book. They touch on it but I am pretty dim witted so....

piston 12 o clock is the front of the piston as if it was installed in the engine. So example the piston pin is front 12 o'clock and back 6 o'clock

Gaps at o'clock please

1) bottom oil control ring at "  " o'clock

2) oil ring expander ring at "  " o'clock

3) top oil control ring at "  " o'clock

4) bottom compression ring at "  " o'clock

5) top compression ring at "  " o'clock

 

 

 

Edited by Dave WM

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It's been awhile but 12 oclock from what I remember was the windshield then 3 would be driver's side, 6 radiator and 9 passenger's side. There is that little nick showing the front of the cup which would be the radiator.

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Good timing. I'm messing with the same thing right now.

I didn't find "clear cut positions" anywhere either, but I believe the overarching gap position rules go like this:

1) All the gaps should be at a 45 degree angle away from the piston pin center
2) The 4th (bottom) ring and second ring gaps should both be in the same as position
3) The 3rd ring and top ring gaps should be 180 degrees away from bottom and 2nd
4) oil wavy ring gap (expander) should be 90 degrees from all the other rings

Some additional rules, not specifically related to gaps, but since we're talking about rings, it's probably appropriate to mention them here:

5) Put the wavy expander in first and make sure the split portion is titts down, like an "M".
6) The thin 3rd and 4th rings do not have a top/bottom. Doesn't matter.
7) 2nd and top rings DO have a top and bottom and make sure you have identified that and get them on correctly.

So, interpreting those rules... Put the waver scraper ring on first. Pick a position for the gap. The rule is "45 degrees from piston pin", so you have four choices - 1:30, 4:30, 7:30, or 10:30. And then once you have picked a position for the expander, the rest of the positions should fall into place.

An example:

Put your wavy expander at 4:30. This mean that all your other gaps must be at 1:30 and 7:30. Fourth and second being the same at either 1:30 or 7:30, but third and first must be opposite.

I looked closely at my block and tried to figure out where the rings originally were from the factory and then when I put the new rings in, I tried to put them somewhere ELSE this time. Figuring I would "even things out". Not sure it makes much difference, but that's my plan.

Before I put the rings on, I marked the piston tops with sharpie to make it easier for my little brain to keep things straight while moving the gaps around. I'll clean the sharpie off after the pistons are installed. Looks like this:
P1160877.JPG

However, all that said, please note that I'm no expert in such matters and give a little time for other people to throw their bodies in front of advice before you put all your pistons in. I'd like to give other people some time to tell me just how wrong I am before you go and repeat mistakes that I've made.

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It would be interesting to see where they are on an engine being disassembled.  I think that they "walk" over time anyway.  I thought that the starting offset was more just to improve the odds of not grooving a cylinder wall or getting poor sealing.  I don't know though.

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My understanding is that the starting offset was to maximize the length of the path between compression and non-compression. The longer the labyrinth, the less leakage. And staggering the gaps +180,  -180,  +180,  -180  is the best you can do.

And while some things are designed to "walk", I don't think the rings are one of them. I believe the gaps are intended to stay where you put them.

But all of this is why I'm hoping some of the engine builder experts will chime in. I have all my rings on pistons but haven't put the pistons back in the block yet. I still have time to completely change all my gap locations if someone throws their body in front of what I'm planning.

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I’m no expert but play one on TV.

I did mine per the FSM. The 77 FSM doesn’t mention the oil ring but the 82 FMS does.

cd6f23cc5b377203397b065f765fa6aa.jpg
You need to be careful when using the ring compressor when installing them as it will cause the rings to migrate. I had to redo a couple. You’ll need to verify them afterwards. You can either use a d flashlight or rotate to crank and look for oil witness marks. See attached pics.

17a8820507d76deed4c2836f440223c5.jpg
6660bc3b5f5f41d5dba8ab413b26363f.jpg
b5c64c4e33172c28c603ab389c581c18.jpg


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I find the pictures from all the FSM's a little confusion because they don't put the FRONT notch up top. All those FSM manual pics have the piston pin running side-to-side instead of top-to-bottom, and I just find it confusing because I want the notch at the top. To get the FRONT notch at the 12:00 position, you have to rotate that sketch. And also interesting to note that they do not specify "FRONT" at all. Just the piston pin direction. Seems it really doesn't matter which is FRONT. You could rotate that sketch either direction and it would still be right.

I rotated it and put on the two possible FRONT notch locations:
ring clocking.jpg

Either of those FRONT locations would follow the "rules".

The FSM shows the pressure rings all at 4:30 and 10:30, but I don't see any reason why 1:30 or 7:30 would be any different.

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2 hours ago, Captain Obvious said:

And while some things are designed to "walk", I don't think the rings are one of them. I believe the gaps are intended to stay where you put them.

My point was about what happens, not what was designed to happen.

Many two-stroke engine pistons have a peg in the groove and the ring ends are shaped to fit the peg.  that's a design meant not to walk.

http://m.2strokeengine.net/gordonjennings/twostroketunershandbook.php

image.png

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My thoroughness is letting my coffee get cold...

https://fpsdistribution.com/articles/piston-ring-gaps-preventing-engine-damage/

"

Aligning Ring Gaps

Unless pegged, all piston rings slowly rotate round in their grooves while the engine is running. For this reason, it isn’t important to make sure the ring gaps are aligned – though you may find it easier for fitting if you stagger the ring gaps before you apply a ring clamp. However, no harm will be done if the gaps temporarily align in service.

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3 hours ago, Captain Obvious said:

I find the pictures from all the FSM's a little confusion because they don't put the FRONT notch up top. All those FSM manual pics have the piston pin running side-to-side instead of top-to-bottom, and I just find it confusing because I want the notch at the top. To get the FRONT notch at the 12:00 position, you have to rotate that sketch. And also interesting to note that they do not specify "FRONT" at all. Just the piston pin direction. Seems it really doesn't matter which is FRONT. You could rotate that sketch either direction and it would still be right.

I rotated it and put on the two possible FRONT notch locations:
ring clocking.jpg

Either of those FRONT locations would follow the "rules".

The FSM shows the pressure rings all at 4:30 and 10:30, but I don't see any reason why 1:30 or 7:30 would be any different.

Isn't it notch towards the front, # to the left of the notch and oil squirt hole on the passenger's side? 

Monroe's book page 125.

20200525_135430.jpg

 

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Posted (edited)

I'd guess that the fact they never specified front or back, only thrust direction, means that it doesn't matter.  Looks like they're just saying "don't line your gaps up with the thrust direction, make sure top and bottom ring gaps are opposing, and put the spacer gap between the two."

They used the same picture all the way through 1983, even with the turbo engine.

p.s. I see that I confused the oil ring discussion with the overall ring gap discussion.  Sorry about that.  Still, it's looking like it doesn't matter much.  Space the gaps out and expect them to move during usage.

p.s. #2 - it would still be neat to see where the rings are in a high mileage engine.  The dynamics might cause them all to end up in a similar position.  A "resting" place after their walks.

image.png

Edited by Zed Head

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This is the instructions that came with my Nissan OEM rings.

ea98b976e93e4d0fd5cf5fbd5cf71a15.jpg


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Posted (edited)
4 hours ago, Captain Obvious said:

 

 

21 hours ago, Dave WM said:

 

Gaps at o'clock please

1) bottom oil control ring at "7:30  " o'clock

2) oil ring expander ring at "4:30  " o'clock

3) top oil control ring at "1:30  " o'clock

4) bottom compression ring at "7:30  " o'clock

5) top compression ring at "1:30  " o'clock

would be CO's pic with the piston marked on top if I read it right. This keeps the gap at 180 out as much a possible with adjacent rings (except for the oil spacer which I presume has no sealing effect so does not matter really).

 

 

 

Edited by Dave WM

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Zed Head, I looked into the ring rotation a little, and you're right. Pretty much everyone says they rotate unless they're pinned in place. So knowing that, it seems to make the importance of the clocking of the ring gaps less important.

One opinion I dug up said that it makes it easier to compress the rings evenly and install the pistons if the gaps are staggered. Another opinion was that it mattered in the initial start first few seconds of the initial start and then doesn't matter at all after that. In any event, I guess I'll keep doing what I'm doing, but won't get anal about nailing my 45 degrees exactly every time.

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5 hours ago, Dave WM said:

1) bottom oil control ring at "7:30  " o'clock

2) oil ring expander ring at "4:30  " o'clock

3) top oil control ring at "1:30  " o'clock

4) bottom compression ring at "7:30  " o'clock

5) top compression ring at "1:30  " o'clock

Right. That's what I'm doing.

The oil expander ring does not contact the cylinder walls at all, so there's no sealing implications there at all. I do suspect, however, that (because of friction) the bottom rings may not rotate at all, or if they do, I suspect they will all rotate together as a set.

So my read is that it's important to get the two lowest ring gaps 180 out of phase, and the expander at 90 between those two. And I wouldn't be surprised if they always stayed that way.

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On ‎5‎/‎25‎/‎2020 at 10:34 AM, Av8ferg said:

You need to be careful when using the ring compressor when installing them as it will cause the rings to migrate. I had to redo a couple. You’ll need to verify them afterwards. You can either use a d flashlight or rotate to crank and look for oil witness marks.

Yeah, I remember our discussions about that and I wanted to let you know where I am at this point...

I only put one piston back in the block, and it was a PITA. Like you, I found the band style compressor to be very finicky. I'm assuming it gets better with experience, but it took me three tries to get the first piston back in without catching one of the oil rings on the block deck. Third time it snicked into position, but I'm just not happy with the compressor. I've actually got two of them and I'm not completely enamored with either of them.

So I decided to try something different and made myself a tapered installation ring tool.

Bought some steel tubing of appropriate size. Here's what I started with, Band tool on left, and thick wall tubing on the right:
P1160945.JPG

I chucked the tubing up in the lathe and bored it out to be a precision fit over the piston:
P1160948.JPG

And then I tapered one end with a gradual taper and polished everything up so the rings slide easy:
P1160952.JPG

The concept is you can slip a fully ringed piston into it and the rings will compress as you push the piston down the tapered section:
P1160954.JPG

And once the rings are all compressed, the theory is that I can just slip the pistons into the bores from here:
P1160964.JPG

And why does this pertain to ring gaps? Because since you're pushing straight down, the gap positions don't migrate. They stay where you put them.

So I'm jumping the gun here a little since I haven't actually used it to put a piston into the block yet, but it worked great on the bench. What could possibly go wrong? go wrong? go wrong?

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ok yul...

nice work. Do you free hand that taper? I only have a small lathe all manual controls.

 

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I have tool and talent envy. Good job. I have a hammer and vice grips .


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Using the lathe to make a thick wall funnel is cheating!! ^_^

I have the band style spring compressor. You have to get them very tight and tap the piston through with the butt of a hammer handle. They also have to be kept tight to the deck. I normally don't struggle too much with them but I have done quite a few this way

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Well nobody get too envious yet. I've not actually tried it for real yet. I'll be sure to keep everyone posted if it actually works.  And a note about the tool... I made that one, but I didn't come up with the idea. I've seen them used in videos in the past, and they are available for purchase cheap in the sizes we would use for our engines.

So, why would I go through the trouble of making one when I could just buy one for $40? The answer is I wanted one made out of steel, and I also wanted to put a little lip on the bottom side to fit into the chamfer recess on the block deck. The commercial ones have a flat bottom where they contact the block, but what I made has a little ridge on the underside that I'm hoping will make it even easier for the rings to make the transition from the tool into the block. Like I said, I'll let everyone know if it works, or was a time wasting fail.

Dave, I did not freehand the taper. I used the compound slide on the lathe. It's got maybe a three inch working throw there, and I only needed two. The most difficult part of the whole job was getting a good polished finish what won't snag a ring. I don't have carbide boring tools, so had to use HSS. And because of that, I had to run very slowly. And I still smoked the cutting oil. It took a while to hit on a tool grind geometry that would cut and not "tear", but I finally did. But even so, there was still a lot of hand polishing required to remove the tool marks.

The REAL way to do this would be to cut on the lathe a little undersize, have it heat treated, and then final grind to size. I'm not really setup for that. And (for the foreseeable future), I only need to get twelve shots out of the tool. Six for me, and six for my buddies build.

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3 hours ago, Patcon said:

Using the lathe to make a thick wall funnel is cheating!! ^_^

I have the band style spring compressor. You have to get them very tight and tap the piston through with the butt of a hammer handle. They also have to be kept tight to the deck. I normally don't struggle too much with them but I have done quite a few this way

LOL  I have a lathe and I'm not afraid to use it.

So about the band style... I actually have two of them. First one I am borrowing from the super-generous hoover @240260280. It uses an infinitely adjustable friction based holding "latch" to keep the size you crank it to. I have a hard time with it though because the latch is quite stiff and it takes a lot of force to crank it down and a lot of force to release the latch. I find it cumbersome and needs three hands to use.

The second one I have uses a ratchet-gear based latch. It's easy to turn, but the problem is I get it tight to the piston, and I really need ONE MORE CLICK. But I can't GET one more click. So when I relax on the tightener, the clamp relaxes a tiny bit and I think that's why I kept snagging oil rings on the deck.

And the other problem with both of them is the area where the spring band overlaps. It's never completely round. I was thinking I could cut off some of the extra metal band to take care of that, but wasn't sure if it would be that much better.

Anyway, after all the futzing with both band style tools, I remembered seeing the tapered style and figured I would give that a try. It took three hours to make, and if I can get six straight shots out of it without worrying about snagging an oil ring, then I'll be satisfied.

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3 hours ago, Patcon said:

I have the band style spring compressor.

Me too, do you also have the scars from the razor sharp spring steel? The bag I store it in is covered in dried blood.

CO, that looks like a good winter lathe project.

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Tens -- maybe hundreds -- of millions of engines are manufactured annually  -  cars, trucks, motorcycles, chainsaws, leaf blowers, what have you.  A complete six-cylinder engine probably gets assembled in net 15 minutes.  I wonder what's used at the factories to compress the rings?

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Namerow, Funny you ask that. I first saw that kind of tapered ring compressor tool on TV. Don't remember exactly what show it was, but probably something like "How It's Made". which is one I watch a lot. I took a quick look through some of the episodes I could find on youtube and didn't find exactly the one I remember, but I did find all sorts of piston installation techniques.

Here's some quick clips with some examples:
https://www.youtube.com/watch?v=0clb7aTYn5o - At approx. 2:15, they use a tapered ring, and the neat thing is that due to the way they attach the piston to the crank first, their tapered ring has a slot in it so they can slip it out of the way past the rod after the cylinder has been slipped over the piston,

https://www.youtube.com/watch?v=Ub0xP9tUzr8 - At approx. 1:30 they use a funky pliers style clamp in one hand while pushing the piston into place with the other. Not a tapered ring, but pretty cool. Looks like it works great.

https://www.youtube.com/watch?v=GUo7qOVycvs - At approx. 3:25 they use a tapered collar style.

I can't remember where I first saw that tapered collar style, but it was a production facility. I think I saw a whole bank of pistons being inserted at once through multiple tapered holes in a jig. I couldn't find that one, but that's what I remember.

So IMHO, the whole drawback to the tapered ring style is that it only works for one piston diameter. If you're only planning to do one or two sizes most of the time, it would be worth it, but if you have no idea what's coming in the door next week, you'd probably just get to be an expert with the spring steel band style.

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12 hours ago, grannyknot said:

Me too, do you also have the scars from the razor sharp spring steel? The bag I store it in is covered in dried blood.

Haha!! Since I have two of these band styles, I may try modifying one (the one that isn't borrowed) to make it a little easier to use and work a little better.

And I thankfully found the sharp edge burr on that thing before it found me. So stupid. For the fifteen second quick wipe across a band sander is all it would take to dress that burr off. That kind of stuff drives me nuts.

So if you do spin one of those up in the winter, let me know if you want any input when the project comes around.

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