Ring Gap?

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93ragtop

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I am working on a 2000 5.9 engine. So far, I have honed the cyl. replaced the cam brgs, and installed a reman. crank and bearings (turned 10-10) from advanced auto.
Now, to my question.
I have a set of Enginetech rings. M40018-STD. Using the orig. pistons.
The FSM says the gap should be .012-.022 on top ring and .022-.031 on second ring.
When I slide the top ring in, it is .026 to .027. Pretty even the whole way, till I go all the way to the bottom where nothing has run. There it is still .024. So according to specs, its too loose.
The second ring measures .021...... which should be .022-.031.

The motor is going back stock, other then a carb intake, holley 670 and maybe headers.
Only drive about 4000 miles a year.
Is the top ring being .026 (specs say 012-.022) going to cause problems?
Should I open the second ring to at least as large as the top ring?

Thanks for your advice.
 
Thats about how my last 5.9 measured with a set of hastings moly rings. That motor is being set up for nitrous, so i gapped the 2nd at .029 sent it on its way.
 
Turboking, first, thanks for the quick reply!!
In your opinion, to you see the extra gap causing much loss of compression, blow by, or burning oil?
Again, it is a stock motor, going to put it in my 87 dakota.
 
I havent had a chance to run that motor yet, still putting the heads together.

As long as you orient the rings correctly and the rings seat properly, i doubt youll see any adverse affects.

Ill let others chime in who have run motors with that much gap for a definitive answer though.
 
The gap is okay as long as it’s consistent from top to bottom of the cylinders stroke. It’s when you run into taper from the top to bottom of the ring travel that you’ll loose seal. How consistent is the gap from top to bottom?
 
Manufactures set standards because they have engineers and research to back it up. It is best practice to follow their advice. Now that's not to say that there aren't other people doing other things that (get by) work. Such as knurling pistons or valve guides. But not in my motor that I want to hold together and last. Build it right or build it twice. And yes, I agree with others. Bore taper is more important.
 
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So your top ring is average .009 over end gap spec. There was an article in one of the mags a while back where they built a motor, new, with huge end gaps. Didn't make much difference. The key is that your bores are straight and round with no taper, as mentioned above. I might file .002 out of the second ring and not worry about the top.
 
If I was going to just tool around on this engine, I'd not worry over it. KB top ring gap specs are just like what you are finding and no one is complaining about them.

My son's 340 has the same sized ring gaps as you are finding on KB's, and it seals up just fine. And, I just put together a 4 banger with the bores enlarged for the use of some forged pistons and got the same range of ring gaps as you are finding. After 50 miles, the cranking compressions were 164 to 169 psi. So the rings are doing quite well and that gap is obviously not any issue at this point in time.
 
If anything, the KB really needs the wider gaps to safely live. Many posters here who have failures related to running too tight of a gap with the hyper pistons.
 
Garrett Ellison said:
If anything, the KB really needs the wider gaps to safely live. Many posters here who have failures related to running too tight of a gap with the hyper pistons.
Click to expand...
The KB pistons mentioned have the top ring up very high on the piston so it sees a lot of heat. The heat causes the top ring to expand and that is why KB recommends a larger gap on the top ring for those pistons.
That said, the folks mentioning that taper is of more importance than the slightly OS ring gap are on the right track.
The slight increase in ring gap observed by the original poster will not be enough to impact blow by or compression assuming that bore geometry and size are with in specifications.
 
File fit rings .005 over
Though I probably wouldn’t worry about it, and put the rings in that are a little over spec, as I always pull a fresh engine down after a season or two max of running, and take a peak inside, and usually new bearings and rings and lap the valves in again.
A customer I usually can’t talk them into this process, and would put file fit rings in to begin with. I keep them to the minimum of spec, and ask to break them in easy.
 
gap kb piston rings per KB
OP you should be fine if non kb pistons no nitrous etc
if kb chrck kb specs or risk pulling your ring lands apart
on b it's nonly high ring but the expansion of the piston and the heat transfer/ retention in the piston that heats the ring
I helped in the design on the quench dome piston- really works lots of dyno time
enjoy
 
Don't think your ring gap is too large. Had a 47 plym coupe with a 400 that I bought as a fixer-upper. Tore the engine down as it was using a lot of oil. All rings had a gap of .125 (1/8 in) and all gaps on all pistons faced to the front. Turned out that the oil consumption was due to a reused valley/ intake gasket. A bit larger gap in my opinion is no big deal on a driver.
 
Garrett Ellison said:
The gap is okay as long as it’s consistent from top to bottom of the cylinders stroke. It’s when you run into taper from the top to bottom of the ring travel that you’ll loose seal. How consistent is the gap from top to bottom?
Click to expand...


I rechecked the gaps. The most I see is .001 difference in the area where the rings touch.

Im going to put them in, Ill file the second ring a little....

FWIW the one thing that bugs me, on the top ring, spec is .012 - .022, and when I check, all the way down in the bottom of the cyl. its still .024. and then the second ring, (which is supposed to be wider then the top) is .018.
Makes me wonder about the enginetech rings.....

Thanks to everyone for your help!!
 
93ragtop said:


I rechecked the gaps. The most I see is .001 difference in the area where the rings touch.

Im going to put them in, Ill file the second ring a little....

FWIW the one thing that bugs me, on the top ring, spec is .012 - .022, and when I check, all the way down in the bottom of the cyl. its still .024. and then the second ring, (which is supposed to be wider then the top) is .018.
Makes me wonder about the enginetech rings.....

Thanks to everyone for your help!!
Click to expand...
You have a picture of the 1st and second ring?
 
93ragtop said:
I am working on a 2000 5.9 engine. So far, I have honed the cyl. replaced the cam brgs, and installed a reman. crank and bearings (turned 10-10) from advanced auto.
Now, to my question.
I have a set of Enginetech rings. M40018-STD. Using the orig. pistons.
The FSM says the gap should be .012-.022 on top ring and .022-.031 on second ring.
When I slide the top ring in, it is .026 to .027. Pretty even the whole way, till I go all the way to the bottom where nothing has run. There it is still .024. So according to specs, its too loose.
The second ring measures .021...... which should be .022-.031.

The motor is going back stock, other then a carb intake, holley 670 and maybe headers.
Only drive about 4000 miles a year.
Is the top ring being .026 (specs say 012-.022) going to cause problems?
Should I open the second ring to at least as large as the top ring?

Thanks for your advice.
Click to expand...
It's a re ring, just make sure the bottom tight spot doesnt close the ring gap below spec and you're good.
Fwiw I never run a bigger second ring Gap than the top I almost always leave the second ring within a stock spec until nitrous comes into play. Those are hyperuetectic pistons and do require more gap to compensate for the heat the piston puts into them. Hypers deflect heat, they are high silicon content and dont really grow at all...so the ring, which is iron or steel grows instead and the gap closes, rings can butt ..and the piston head comes off.

Second ring @.018 is fine...or .024 will work... not ideal, but you wont know the diff.
.028 top ring sounds good.
 
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If you’re not boring, always go with file-to-fit rings... what you have is normal with worn stuff.
Because you have it all, just assemble what you have. It will be fine.
 
my68barracuda said:
The KB pistons mentioned have the top ring up very high on the piston so it sees a lot of heat. The heat causes the top ring to expand and that is why KB recommends a larger gap on the top ring for those pistons.
That said, the folks mentioning that taper is of more importance than the slightly OS ring gap are on the right track.
The slight increase in ring gap observed by the original poster will not be enough to impact blow by or compression assuming that bore geometry and size are with in specifications.
Click to expand...

The KB's have a lower top ring placement--KB's ring gap requirements are not based on the ring groove placement. Its the alloy. KB's get a bad rep from some and yet the only KB I've ever seen broken was my own and I knew I was hurting it when I had my foot buried and could hear the "can full of marbles" . High load and thus high heat will exceed KB's ring gap spec's in a hurry.

To the OP--I hope you were able to put a nice cross hatch on the cyl's and limit taper. If you used a rigid hone like a Sunnen AN series then your job was much easier--If you used a spring loaded 3 finger deal then I strongly doubt you will have much success. J.Rob
 
RAMM said:
The KB's have a lower top ring placement--KB's ring gap requirements are not based on the ring groove placement. Its the alloy. KB's get a bad rep from some and yet the only KB I've ever seen broken was my own and I knew I was hurting it when I had my foot buried and could hear the "can full of marbles" . High load and thus high heat will exceed KB's ring gap spec's in a hurry.

To the OP--I hope you were able to put a nice cross hatch on the cyl's and limit taper. If you used a rigid hone like a Sunnen AN series then your job was much easier--If you used a spring loaded 3 finger deal then I strongly doubt you will have much success. J.Rob
Click to expand...
Actually when I spoke with the KB on line tech he mentioned the high top ring location as being the reason for the larger top ring gap. He said that in operation the heat will cause the top ring to expand and the ring gap in
operation will have near the same gap as a typical top ring. The second rings gap installation recommendation is about the normal ring gap to bore size ratio.
It seems to me if the piston was expanding it would be the piston to bore size ratio that would be significantly adjusted and result in a larger piston to bore clearance at installation. And as the piston expanded it would take the piston ring with it and enlarge the end gap,,,
 
my68barracuda said:
Actually when I spoke with the KB on line tech he mentioned the high top ring location as being the reason for the larger top ring gap. He said that in operation the heat will cause the top ring to expand and the ring gap in
operation will have near the same gap as a typical top ring. The second rings gap installation recommendation is about the normal ring gap to bore size ratio.
It seems to me if the piston was expanding it would be the piston to bore size ratio that would be significantly adjusted and result in a larger piston to bore clearance at installation. And as the piston expanded it would take the piston ring with it and enlarge the end gap,,,
Click to expand...

I guess he doesn't really understand his product totally. I have provided a photo of a KB on the left and a Mahle forging on the right. The KB has a top ring land of .280" and the Mahle .240". The Mahle does not require any additional top ring gap unlike the KB. If its placement and not alloy type as you and KB suggest then please explain. I'm curious now. J.Rob

Topringplacement.jpg
 
An interesting question indeed. A quick look at the material says that is not likely the difference: thermal conductivities of hypereutectic AL in one study are as high or higher than 2618 AL for all hyper mixes. Conversely, this product sheet shows it to be 13% lower than 2618. So not a huge factor either way. AMC 4632 - Hypereutectic, high tensile modulus aluminum silicon alloy

I would suggest looking at the heat path from the crown down into the rest of the piston. The KB pix above shows the large gap between the top and 2nd ring, and the large round groove between them. The crown thickness in the KB's is not all that thick... maybe in the range of .225-.250" (as opposed to older style cast pistons as an example, where it is commonly .300" thick or more). So with that thin crown, the longer path down into the skirt, and that extra round groove helping to restrict the heat flow path, it may be that the crown and top groove on the KB's just runs hotter due to a poorer heat conduction path. That would put more heat in the top ring.
 
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