Piston Ring Gap [Merged 5-7] gapping rings pistons end filing

[fourreGsixty3]

The piston's, and ring's should have been measured first so that there wouldnt be a mistakes like this to occur, and each cyl. would have been matched to each ring/piston combo. Im guessing that you are using the feeler guage after the piston/ring's are intalled to check the clearance between the ring/cyl. wall. Also you have to take into account that the top section of the piston where the ring's are situated expand's when at OT so some of that gap will be closed some.

 

[Big Woo]

Well this happens quite often, mostly because people don't check the ring clearence.

If you want your rings end gaps perfect then you need to purchase an oversize or file fit ring set. There is one variable that the piston and ring manufacturers have "zero" control over, and that is finish bore size. Therefore "pre sized" rings sets are sized to ensure that the ring gap will be sufficient, and that the ring ends will never touch each other.

 

[boosting_laser]

UPDATE:

After cleaning, measuring, grinding, measuring, cleaning & installing the new set I'm a happy camper. These had a lot more "meat" on them to grind away, then the ITM's. I did notice the ITM set did look identical to stock, whereas the Hastings take a total different design.

Well....on with my build, which seems will never end!!!!!

 

[snailspool]

After reading through some articles i had decided that the best ring gap for me whould be a .19 #1 ring and a .23#2 ring. When i measured my gap, right out of the box though my top ring was a .020 and ring 2 was a whopping .29 . Now ive read that a larger than normal 2nd ring gap will prevent high rpm flutter, but is this too much? What kind of adverse effects will this cause? The motor in build is a 1g rod, 2g .20 oversized pistons, with a 50 trim running 23psi on the street and 28 at the track. I do plan on DD it. Thanks.

 

[steel_3d]

What brand rings are they?

I'd say you'll be fine. Some others might too: http://www.diagnosticengineers.org/Page B5-37.htm

 

[snailspool]

They are NPR rings (nippon piston racing).

 

[sawnuoff]

most ring manufacturers will give you guidelines to follow depending on your engine demands like turbo, spraying it, drag racing, stuff like that, now i went stock in my stuff and went with whatever the factory says except for the 2nd ring i made mine the same as the top ring gap, because the top is taking all the heat the 2nd ring could be even a little tighter if dare try that i wasn't to sure myself so i went with the same as the top. i have no troubles. the top ring will gets alota abuse which i think is why the 2nd ring can be set a little tighter, to me looser would be just about wore out again, but then it depends what your plans are with the motor, dont set them for turbo only, plan ahead.
i'm not sure what dd means either.

you may want to contact who made those rings to ask them they are experts.

 

[snailspool]

well, the rings did not come with specs. I tried to get a hold of the seller but to no avail. DD means daily driver so if i lose just a little power and am not smoking or putting oil in every 2 weeks i can live with it. Any other opinions?

 

[AWDJDMTALON]

I have a ring problem. I am using .020 over Manley pistons. The block was bored .024 per manley.

Here is the problem. With the top compression ring installed, the piston will hardly move. I set the ring gap at first to manley's spec. .004 gap. No good. Then I used factory spec. set at .012. still no good. Then taked to Mike at SBR. He recommended .019. Set to that spec. still no good. It takes a lor of effort to get the piston in the bore at all ring gap settings. If I remove the top compression ring the piston moves freely w/ slight resistance by hand. Feels like the stock stuff did on dissasemble.

I measured the ring to piston clearance. I think (it was 2 days ago when I was doing this) the factory spec was .00015. Well I have no measurable clearance.

The rings are the ones that came w/ the pistons. I think that Manley put the wrong rings in the piston kit.

Anyone else have this probelm?

 

[brute]

You are compressing the rings, right? What type of compressor are you using? Is it hard to get in while you're pounding the piston in, or what is going on with that?

For what it's worth, I have Topline 0.020 overs, and using the rings that came with them. It was suggested to me that I do 0.019 as well, and mine went in fine.

 

[AWDJDMTALON]

Thanks for the help. It was late when I was doing this, and got the two compression rings swapped in the lands. So 2 was in 1 ect. Got it fixed now and they went in beatufully.

 

[tsunari]

Okay . . . hopefully this thread will settle or at least shed some light on the two theories for what piston ring gap to run on boosted applications.

Theory 1 -- Top ring gap should be SMALLER than 2nd ring gap

Premise :: In doing this, any gases that actually make it past the top ring should more easily pass by the second ring. This is supposed to help keep the top ring sealed and prevent ring flutter resulting in more potential power.


Theory 2 -- Top ring gap should be LARGER than 2nd ring gap

Premise :: This is done because the top ring takes the brunt of the forces seen in the power stroke and therefore may expand more than the 2nd ring. Because of this, one should gap it a little wider in an attempt to prevent the ends of the rings from ever coming in contact.


So which is it?! Anyone have some good 1st-hand experiences (good or bad)

 

[My96AWD]

it is theory 1.

 

[topstreet]

Here is a good read:

Author Larry Carley

RETHINKING RING GAPS
The old school philosophy of engine building said the end gaps on second compression rings could be tighter because the number two ring is not exposed to as much heat as the top ring. The new school of engine building says it's better to open up the second ring gap a bit so pressure doesn't buildup between the rings and cause the top ring to lose its seal at high rpm. The result is better compression, better piston cooling and reduced oil consumption. Any pressure that builds up between the rings will blow down into the crankcase, keeping oil out from between the rings.
Getting rid of the end gap altogether can also improve sealing, cooling and horsepower. Some engine builders who have switched the rings they use to a set that includes a "gapless" top compression ring say they've gained three to five percent more horsepower with no other changes. Gapless rings are available in popular sizes with various wear-resistant face and side coatings. On some engines, the second compression ring can be eliminated if a gapless top ring is used. Getting rid of the second compression ring cuts friction and adds horsepower, too.
SMOOTHER, FLATTER
Another trend that seems to have additional benefits is the use of smoother, flatter rings and pistons with precision machined grooves. Once ring supplier says their racing rings are manufactured to within 50 millionths of an inch flatness and parallelism, with a finish that is typically 4 Ra microinches or less. This allows tighter assembly tolerances for better performance.
With some low priced pistons and ring sets, there is a certain amount of waviness that concentrates contact between the rings and lands. This encourages microwelding the groove pound-out at high rpm.
Friction-resistant coatings on the sides of the rings and/or ring grooves in the piston can help prevent this from occurring.

If you actually read this then you would see that the opinion of the author is to have a larger 2nd ring gap on an engine like the modified 4G63. I would agree.

Jake H

 

[TSIfreek]

I agree with jake as well. The top ring is your main compression ring and your second is more of a oil scraper . Ring gap on the second ring should be larger to help in getting any excess blow by threw the second ring to prevent the top ring of loseing its seal. This is very important of high boosted engines were cylinder pressure is very high.

 

[tsunari]

I'm definitely starting to agree with the tighter top ring theory . . . Doing some more research, I found the following talking about Perfect Circle Piston Rings in a Clevite catalog:

"Notice: Most of the second ring gap recommendations are larger than the top rings. Recent testing has proven that a larger second ring gap increases the top ring's stability allowing for a better seal. This larger "escape" path prevents inter-ring pressure from building up and lifting the top ring off the piston allowing combustion to get by. Many engine builders have reported lower blow-by and horsepower gains at the upper RPM ranges with the wider second ring gaps. Also, almost every new car made is using this inter-ring pressure reduction method to lower blow-by and emissions and to increase engine output."

Couple that will all of the great feedback on this site and I'm definitely sold!

Thanks for the great feedback guys.

 

[tsunari]

Another question to follow up:

Seems as though the consensus on this site is to run a top ring gap around .020" and a 2nd ring gap around .023". Why is this when the stock gap ranges are:


DSMtuners:
#1 ~.020"
#2 ~.023"

1G:
#1 .0098" - .0157" [Limit .031"]
#2 .0079" - .0138" [Limit .031"]

2G:
#1 .0098" - .0138" [Limit .031"]
#2 .0157" - .0217" [Limit .031"]

Is this just because the factory recommendations are for factory pistons, ring, boost settings?

 

[diambo4life]

Another question to follow up:

Seems as though the consensus on this site is to run a top ring gap around .020" and a 2nd ring gap around .023". Why is this when the stock gap ranges are:


DSMtuners:
#1 ~.020"
#2 ~.023"

1G:
#1 .0098" - .0157" [Limit .031"]
#2 .0079" - .0138" [Limit .031"]

2G:
#1 .0098" - .0138" [Limit .031"]
#2 .0157" - .0217" [Limit .031"]

Is this just because the factory recommendations are for factory pistons, ring, boost settings?

Yes.

Not to mention that most "performance" aftermarket pistons are forged. Thermal expansion properties will differ from those of cast pistons. On heavily boosted motors with high HP, PLUS is always better than tight.

Ring gaps will be dependent on application. There is no "set" ring gap to go for. Nitrous applications for example will call for bigger end gaps and different piston manufacturers will call for different end gaps depending on setup and goals.

 

[wortdog]

Yeah, the Tuners general recommended values match the numbers I got from running the equations given in the instructions with my Ross stroker pistons of 0.0194 for the top ring and 0.02283 for the bottom ring on a thin ring (less than .180in), high-cylinder pressure engine.

The equations they give for the top ring gap should be (bore size(inches) x .004) + .002(for thin rings) + .004(for high-pressure turbocharging).

The bottom ring is just (bore size(inches) x .005) + .002 + .004.

These are just an example of course, but most of the piston ring manufacturer's recommendations will be similar.

 

[groundPork]

One thing I'd like to add (which supports other posters in this thread) is not to confuse the larger second gap as a substitute for what top ring gap you may have. The top ring gap is almost entirely dependant on the amount of heat it has to try to cope with due to the chamber temps. When a piston ring is exposed to heat it's material expands (different materials and grades of materials have different expansion rates). The main reason for more gap for higher heat situations, is becasue the ring actually increases in circumference as it expands, not just in axial and radial width. This means if you straightened it out it would acutally be longer under thermal loading as apposed to ambient temperature or colder. This is how the rings can potentially end up touching ends. if that happens the result could be as mild as scuffed ring faces or pistons, to actually locking everything togather and virtually yanking the tops of the pistons off.

My point being that the top ring just needs to be gapped what it needs to be gapped to. The second does not need to be gapped to prevent butting so much, as just to allow blowby gasses to bypass the second with as little resistance as possible.

Almost all modern ring sets incorporate symmetrically barrel shaped top ring face profiles which really only seal well when force from combustion gasses are applied to the back. they really don't stop oil from entering the chamber at all becasue of the very profile. The second rings usually are asymmetric on the face to form a squeegy like scraping ring, but the can allow blow by to easily pass or even overide them if it is bad enough. Oil rings are also symmetric in face profile, and are nothing more than scrapers which remove the majoiry of oil slosh from the cylinder walls through not much more than virture or radial ring tension against the cylinder. Oil rings DO NOT BED IN... second rings due to a certain extent, and top rings due, and top rings due the majority of wearing in the bore surface itself. Try not to confuse gas seal with oil seal. Although it's not widely understood, all three rings have almost unrelated specific jobs, and specific ways in which they perform them. I am including this info especially for those who have done rebuilds, and those who plan to, to possible help you be more informed, should you run into such probelms.

One thing to always remember is that OEM ring and piston gap numbers are based on a known heat range in the combustion chamber that can be controlled as long as it cannot be tampered with externally, once you cahnge anything drastically enough to go outside of the systems ability to compensate, youare out of the safety zone. There rings are no different form the aftermarket, it's the evironment they are exposed to that is.

 

[Girvin]

Just finished searching through pretty much every post on ring gap clearance. Im not sure if there isnt' a solid answer or that everyone has their own opinion.

Anywho, for those running Ross pistons and are making 500whp or more.....what are your end gaps set at? Im thinking of going with a .020 top and 0.23 bottom. Need to solidify my decision.

Any help would be greatly appreciated.

 

[SnowBird]

Me again. I have OEM 20 over pistons and a 20 over block. I checked the #2 rings by putting them in the cylinder and pushing them down with the pistons. Ive only checked my #2 rings because Im stumped on how to get them outta the cylinder. What do I do? Pull the oil squirters and continue to push the rings out the bottom with the piston?

Question 2: My end clearance on the #2 rings are all .029 This is more than the haynes manual says, but Im not sure because these are 20 over, and the manual says more gap is not critical unless its .039 or more. Thanks in advance, the reason Ive only checked these rings is because I dont know how to properly get them out to try the other ones. Thanks.

 

[toybreaker]

Me again. I have OEM 20 over pistons and a 20 over block. I checked the #2 rings by putting them in the cylinder and pushing them down with the pistons. Ive only checked my #2 rings because Im stumped on how to get them outta the cylinder. What do I do? Pull the oil squirters and continue to push the rings out the bottom with the piston?

No, please don't do that. They will expand suddenly when they fall out at the bottom. They could hit the main bearing webbing and break or at the very least you'll ding the sealing edge.

Just put your hands together, fist to fist, then take your fingers of both hands, knuckle to knuckle and go down the bore to the ring. Spread your fingers out to catch a couple of different places on the ring and gently drag them back up the bore as straight as you can.

I've found that laying out four numbered sheets of paper on the floor, and then putting each ring on it's sheet, and writing the measurements down makes this job go quickly, and stay organised.

Good luck, and let us know what the other ones measure out to.

 

[SnowBird]

Thanks for the tip, its just so dam hard to get my hands down there, but I know exactly what you are talking about, Im not gonna worry about my gap being too big as long as the top ring is smaller, but Ill post it. Thanks again for the tip.

 

[Defiant]

The piston is only used to square the rings up with the bore centerline. Notch a couple of dowels to hook under the ring to pull it back out, if you pushed it in so far your fingers won't reach.