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Thread: Piston ring end-gaps too large
12-27-2016, 01:47 AM #1
Piston ring end-gaps too large
I measured piston ring end-gaps and some were too large, including all the oil rings. I have standard bore diameter. Any advice here ?
Some gaps were significantly over spec, including all the oil rings (yes, I measured them far down in the bore, not at the top).
Too small end-gap is way worse than too large, but have a look at these measurements....
#1 compression ring gaps are averaging around 0.016" which is close enough to spec.
#2 compression ring gaps are averaging around 0.019" which is within spec, but one ring is 0.023" and another is 0.039" ! I tried moving these rings to different cylinders.... and its due to that ring being small, not a large cylinder.
Oil ring end gaps are averaging around 0.037" which is way larger than spec.
'82 - '83 specs are:
#1 spec = 0.0083" - 0.0146"
#2 spec = 0.0067" - 0.0209"
oil ring spec = 0.0079" - 0.0276"
Here's that #2 ring with the really large 0.039" gap, you could drive a bus thru there. The cylinder above shows a normal gap.
I'm happy with all the #1 gaps and and those are the most important, but the oil ring gaps are way over, and a couple #2 ring gaps are way over also. These are a Beck/Arnley ring set 013-3867. I don't think my bores are worn out, the machinist said there wasn't much wear.
How big a problem is this ? Seems like the oil rings may not be that big a deal. Should I buy another set of rings to replace some of the short #2 compression rings ?
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12-27-2016, 03:20 AM #2
WELLLL...what we used to do in Ye Dayse Of Olde was to buy oversize rings and file them down until the gap was in spec. Some guys even had a little machine to grind them down so the end-gaps came out right.
I don't know how consistent the rings are out of the package. "Standard" size rings might be all over the map. Have you tried swapping them around in different cylinder bores? I'm guessing that won't matter because the bores should all be the same size +/- almost nuttin'.
I agree that the gap on the oil rings isn't that important. As long as you place the gaps 180* to each other, they should scrape the oil off the wall OK.
#1 ring is critical, and the #2 ring almost as much.
One thing I was always told told was to err on the side of slightly larger gaps. If the ends of the ring butt together, you'll get a broken ring almost instantly, and that's A Bad Thing!1985 5-speed "Ms. Swan"
OH, What A Feeling!
12-27-2016, 03:22 AM #3
Looking at those pix closely, I have to ask:
Was this block bored oversize and honed?
Something about those cylinder bores just looks "funny".....almost like they weren't bored, just honed.1985 5-speed "Ms. Swan"
OH, What A Feeling!
12-27-2016, 09:21 AM #4
- Join Date
- Jul 2015
- Calgary, AB
It's not normal to have that much variance in your 2nd ring end gaps. If it were my engine, it would make me question the entire ring pack and I probably wouldn't use them. I've never used Beck/Arnley rings (and I've built ~500 engines) but I'd be surprised if you had these issues with rings from Hastings or Enginetech.
Also, it's good practice to check ring end gap over the entire cylinder bore when you're doing a re-ring job such as this. Its good to know what the ring end gap is at the top of the cylinder as that is where your compression is made. You're not going to like the number because your cylinder is worn there (you can see the ring impressions) but at least you know what it is.
12-27-2016, 01:54 PM #5
12-27-2016, 02:12 PM #6
Also its weird that these rings don't have markings on them to indicate which side faces upwards, maybe they're bi-directional. The original rings had markings, 1T & 2T.
I'll check the gap along at different depths in the bore like you suggest.
The bores show ring impression markings near the top, but they aren't really deep, I cant feel them with my finger. They show up visually more prominently after the hone.
I'd hate to have to buy another ring set, but if I must I will. Enginetech rings are available at rockauto.com, and are listed as a premium set.
12-27-2016, 02:19 PM #7
I thought the rings would come out of the package too long, and that they could be filed down to fit. In this case there's nothing I can do to make them longer.
I thought that filing down over-size rings which have a different diameter will result in an oblong ring, not perfectly circular.
12-27-2016, 05:05 PM #8
- Join Date
- Jul 2016
I've ordered lots of parts from RockAuto and been very happy with their quality and prices. There were however a couple of times that I received incorrectly packaged parts from them - the part inside the box was not what was labelled on the box.Original owner 82 P-Type, 2JZGTE, AEM, Borg Warner EFR turbo,NW leather seats, BBK, Coddington Wheels, Raptor Racing exhaust
12-27-2016, 05:15 PM #9
I'm learning these things as I go, and I've read that chrome rings are better for turbo (which I'd like to do in the future); the 7MGTE uses chrome rings.
I've also read that fresh re-bored cylinders can use chrome rings, but used bores should use cast rings.
Apparently there are 3 types of rings, moly, chrome & cast.
Moly rings will have a shiny grey OD; chrome rings will have a shiny silver OD and the cast rings will be black in color on all surfaces.
The beck/arnley has cast (black on all surfaces) #2 rings..... the #1 rings are shiny grey on all surfaces, so those must be moly.
12-27-2016, 05:32 PM #10
"Moly" rings have a coating of Molybdenum them. AFAIK, they're just specially treated cast-iron rings. They used to make the face of the ring concave, and fill that depression with Moly which formed the actual sealing surface of the ring. It's been many, many years since I built engines, so I wouldn't be surprised if the technology has changed. They seat very fast compared to chrome-plated rings, which are harder on the cylinder walls.
No experience with supercharged engines, so I can't comment on what type of rings are "better".
All the rings I've ever used were marked with a dot that indicated to "top" side of the ring. I've always bought Perfect Circle or Hastings rings.
I don't think filing the ends gaps will make the rings go out-of-round enough to worry about. It's always been "standard practice" even with the guys that bore and hone with deck plates to make the cylinders extremely round once the head is torqued on the block.
As far as incorrectly marked boxes from Rock Auto, Christina (black MKII from AZ) had a rant on her FarceBook page about getting a load of bum injectors from Rock Auto. So far I haven't had that happen, but now I'm inspecting each package I get from them very closely.1985 5-speed "Ms. Swan"
OH, What A Feeling!
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