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Old 10-17-2010, 04:27 PM   #1
Bad Noodle
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Default DIY Piston Ring End Gap - No funny tools

Thought I'd share what I've learned here.

So here goes.

- First, figure out what your ring end gap should be. Ring end gap is usually based on bore diameter so do your math. Your top and second ring gap will be different based on what pistons your get. For my manley 100mm pistons my end gaps are:

End gap in In = bore diameter in mm / 25.4 * factor from instructions

Top Ring = 100/25.4*0.0055 = 0.0216"
Second Ring = 100/25.4*0.0035 = 0.0137"

So first thing's first, check what you have:

I keep my bores coated with white lithium grease to prevent them from rusting. Works great. Anyway, wipe off about 2 inches. Don't need to clean it with carb choke cleaner since a little oil film is ok:



Put the ring into the bore at the top and use the piston to push the ring into place about an inch down or whatever your instructions say. You want the ring to be square in the hole. Using this piston I lines up the flat underside with the deck of the block ensuring the rings is square.



Next, insert feeler gauges into the gap at the end of the ring until you have one that just barely holds itself up. This is your starting end gap:



Next, you need to practice grinding rings. So after measuring your top and second ring gap, you will work with the ring that needs the most work. For example, my top ring starting gap was .0175" and I need .0215" so I need to grind off .0030". Since this is the first ring I'm going to be doing, need to do some experimenting first. Set before I try to go for .0215" I'm going to see if I can set .0190" properly and if that works out, then go for .0215".

The file setup look like:

When grinding the rings, grind one side only. Hold them so the flat side rides along the vice and when looking down at the ring, the edge is square to the file. This will insure the end gaps stay square. Also, only grind the ring pulling towards you or file from the outer edge towards the inner edge. Do NOT rub it back and fourth.



Use your left had to push the ring against the file and the right hand to keep the edge square. Keeping the edge square takes a little practice which is why you shouldn't grind off too much at first.

If you do really bad, when you hold the ground end of the ring into the light you will see that you're grinding only part of the face. It will looks something like:



If you're grinding the entire face, but not square, when you check your end gap as you should be doing frequently, you will see that the feeler gauge will slip easily into the inner edge but won't move all the way to the outer edge/bore wall. The error looks like:



If you're doing everything correctly, meaning your end gap is set and your faces are square, the feeler gauge should be inserted so that it touches the bore wall, should be a little snug, enough to hold itself up, and the ground faces should be even on the feeler.



Also, be sure you deburr your edges. You're not going to grind off any extra material, you just want to pull off any shards sticking out. I used a bigger dremel grinding wheel and just pulled it lightly against the edges. You can feel it catch the burrs as it moves, so once you can pull it over the edges smoothly, you're good to go.



This will take a while, so take your time. Just for reference, it took me 4 hours to do my rings working at a even pace. Took me about 2 hours to get the setup right and learn to grind them properly, then another 2 hours to do all the rings.
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Old 10-17-2010, 05:24 PM   #2
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great write up! Im just about to tear down and rebuild a ej20 to fit new pistons,rings,and acl race bearings. This will mos def help bro! Thanks!
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Old 10-17-2010, 07:20 PM   #3
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great write up reference, thank you
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Old 10-17-2010, 07:43 PM   #4
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Weird. When I do cp 99.5's I use a .017 top gap and .021 bottom.
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Old 10-17-2010, 09:22 PM   #5
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Quote:
Originally Posted by sidewayz View Post
Weird. When I do cp 99.5's I use a .017 top gap and .021 bottom.
it all depends on who makes the pistons. Manley's instructions say:
Top Second
Bore x .0055" Bore x .0035"

so don't go by my specs. Go by the spec sheet for the pistons
'
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Old 10-17-2010, 09:29 PM   #6
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Oh I wasn't gonna lol. Just thought it was strange that those are that different
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Old 10-18-2010, 07:13 AM   #7
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Quote:
Originally Posted by sidewayz View Post
Oh I wasn't gonna lol. Just thought it was strange that those are that different
10-4 on that buddy. I looked through every piston manufactures instructions before doing this and some of the differences had me
I do wonder why there is the difference, seems like this should be a standard thing. Differences might be due to how the rings are shaped and which way they fit?
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Old 10-18-2010, 10:22 AM   #8
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Nice write up!

I thought this aswell. Its crazy how different the ringgaps can be, between different manufactures...
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Old 10-22-2012, 05:56 PM   #9
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To split the case halves, I like to use the OEM spare jack from the trunk. Once all the bolts are out the gap in the top of the jack (meant for the pinch weld) fits nicely over the rear bottom engine-trans bolt. It will crack the seal very nicely.

-Dave
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Old 10-22-2012, 07:10 PM   #10
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I just measure with feeler gauges like you do then i figure out how much more I need to get my final gap and set my calipers to that measurement and use them to scratch a line on the top if the ring. Then I just grind to the line..... With a bench grinder😱. Works perfect
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Old 10-22-2012, 10:51 PM   #11
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Nice Job!
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Old 10-23-2012, 08:39 PM   #12
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This might be a dumb question but, when you calculate and cut/file the rings per spec does it matter much without the heads being bolted on? I know it only distorts out of round of the cylinder so much as .001" but the specs you have posted above look very precise.

- Dave
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Old 10-23-2012, 08:49 PM   #13
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People advocate the use of a torque plate to size the rings.
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Old 10-23-2012, 09:11 PM   #14
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Torque plate on my last build distorted the top .001" and almost .002" in the middle
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Old 10-23-2012, 09:24 PM   #15
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Well after thinking about it, the circumference of the bore doesn't change when using torque plating, just the shape. Therefore wouldn't the ring end gap be the same with or without?
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Old 10-23-2012, 10:53 PM   #16
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I would assume that, since the bore is now distorted, the ring will follow the shape of the bore, and so the gap will now be tapered with outer edge or inner edge having more or less gap depending on the amount of distortion.
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Old 10-24-2012, 08:44 AM   #17
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You guys do bring up an interesting point. My personal opinion on this subject is that the bore circumference does not change, only gets distorted. Therefore it doesn't matter whether you use a ring grinding tool or this method, both will give you the same results as both grind the rings outside the bore.

I'm not really advocating this method as the best way to get the job done, this is just an option for those that want to build an engine but don't want to buy another $100 tool that they will only use once. I would not use this method if I had access to a ring grinder.
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Old 10-24-2012, 02:05 PM   #18
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torque plate on while doing this is a good idea. also, ring filers are like $30 on ebay.
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Old 10-24-2012, 02:12 PM   #19
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Quote:
Originally Posted by bebesito21 View Post
torque plate on while doing this is a good idea. also, ring filers are like $30 on ebay.
If you're talking about the pot metal base with a hand crank grinding wheel then those are total junk. Do the old fine file or stone in a vise and do it the old fashioned way.
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Old 10-24-2012, 02:49 PM   #20
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Quote:
Originally Posted by Bad Noodle View Post
You guys do bring up an interesting point. My personal opinion on this subject is that the bore circumference does not change, only gets distorted. Therefore it doesn't matter whether you use a ring grinding tool or this method, both will give you the same results as both grind the rings outside the bore.

I'm not really advocating this method as the best way to get the job done, this is just an option for those that want to build an engine but don't want to buy another $100 tool that they will only use once. I would not use this method if I had access to a ring grinder.
If you check out Crystal_Impresiv's thread about torque plates you'll find his data for ring end gaps with and without torque plates. There was a measurable difference in final endgaps with and without the plate and he recomends the gaps be set with a torque plate installed.
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Old 10-24-2012, 03:02 PM   #21
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Quote:
Originally Posted by reid-o View Post
I would assume that, since the bore is now distorted, the ring will follow the shape of the bore, and so the gap will now be tapered with outer edge or inner edge having more or less gap depending on the amount of distortion.
.001 distortion x pi = .003" ring gap change.
.0015 distortion x pi = .0047" ring gap change.
.002" distortion x pi = .0063" ring gap change.

From JE's installation guide: "A diameter variance from one cylinder to the next changes the end gap of the rings
in that cylinder by a factor of pi (3.1416). For example, a cylinder .001 larger in diameter will increase the ring end gap by .001 x 3.1416 = .003,
rounding off, which could increase cylinder leakage in that cylinder and decrease performance"

From CP's installation guide: "RING GAP MEASURING
PROCEDURES
1. A torque plate should be installed on engine (if applicable)
and torqued to same specifications as machine shop.
2. Piston ring should be below and square to the deck.
3. Measure ring end gap with a feeler gauge."
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Old 10-24-2012, 03:05 PM   #22
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BTW setting gaps with a file is completely fine. Just make sure you move the ring away from the body so you dont chip the coating off the rings. Same thing with a grinder, turn torwards your body to avoid chipping. I usually use a grinder to get close and hand file to finish. A diamond blade works much faster then a file.
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Old 10-25-2012, 12:01 AM   #23
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Quote:
Originally Posted by Crystal_Imprezav

.001 distortion x pi = .003" ring gap change.
.0015 distortion x pi = .0047" ring gap change.
.002" distortion x pi = .0063" ring gap change.

From JE's installation guide: "A diameter variance from one cylinder to the next changes the end gap of the rings
in that cylinder by a factor of pi (3.1416). For example, a cylinder .001” larger in diameter will increase the ring end gap by .001 x 3.1416 = .003”,
rounding off, which could increase cylinder leakage in that cylinder and decrease performance"

Your math is off. A distorted circle is an oval. The largest diameter from an oval x pi /= circumference. You must also factor in the smallest diameter.

So .001 distortion x pi /= .003" gap change.....0015 x pi /= .0047"...ect

JE is referring to undistorted cylinders with different diameters, so their quote is correct but does not support your calculations.
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Old 10-25-2012, 04:40 AM   #24
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So OEM again you attack one of the regular members that offers actual help and advice, but you do not offer any alternative advice. All I get out of your post is "you are stupid but I won't tell you the real answer". Look we already know you are anti torque plate...which makes it apparent your shop (what shop is that again?) does not use them.

Regardless of whether it is a circle or an oval, a distorted bore WILL cause problems with ring seal. I do not see why you keep arguing something that has been accepted in the auto industry for as long as many of us have been alive.
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Old 10-25-2012, 08:23 AM   #25
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So maybe someone can help me out here with understanding this but if proper procedure per je, cp,... Is followed and a tq plate is used while honing/boring and tq plate with the same tq values as while machining is used while installing the rings doesn't that negate 99% of the issues of cylinder ovaling that oem is talking about making a calc wrong because it was all machined, measured, filed, whatever under the same conditions, preferably in the same temp with the same measuring tools? I am not trying to be snarky I just would like to have a better understanding.
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