The maximum ring end gap for non-critical applications?

[barnym17]

I know from personal experience that when you are a 15 year old kid who don't know shit from shinola and you put 283 rings in a 327 and never even heard of checking ring gap,you kill every mosquito within 2 miles from the oil smoke cloud.

[cjperformance]

I know from personal experience that when you are a 15 year old kid who don't know shit from shinola and you put 283 rings in a 327 and never even heard of checking ring gap,you kill every mosquito within 2 miles from the oil smoke cloud.

Haha the best mozzie buster in town !!

[crazyman]

I know from my heyday I got a 350 from the JY you could move the piston about an 1/8". I can't imagine that ring gap. Best running cheapie I ever had. Only smoked at startup and around 7000rpm during a one wheel wonder. Obviously aftermarket cam, intake, headers, and home port. PCV delete with VC breather.

[modok]

Seems I took "non-critical" more literally than the others.
The engines I build most often, the second ring gap is .060 from the start, and they don't stop driving until the top ring breaks and the second ring wears to near nothing. Maybe I misunderstood.
Are military and industrial engines critical or non critical?

.060" from the start, what bore size, what application

cummins, 4.016 bore, first that comes to mind, but quite a few are like that, not just diesels.
Probably they are....trying to prolong th elife of the second ring? I assume, don't know.
Top gaps in the heavy duty stuff are pretty consistent new, but they DO WEAR, unlike a lot of the racing and oe quality modern stuff that barely does.

[user-23911]

a few thou too tight can destroy an engine, especially with hypereutectic pistons.

I'll disagree with that statement.

I don't think I've ever broken a piston on an N/A engine.
I've spun big end bearings and thrown rods with a combination of bad tuning and bad building........maybe 40 years ago.

But when it comes to playing with boost, hypereutectic pistons break very easily when you get the tune wrong.
It's the knock that does it............it's got zero to do with ring gaps.
I've broken so many of them that I've forgotten how many.

Where did this myth come from?
Engine builder versus wannabe tuner.
Tuner blows it up because he got it wrong..........it wasn't strong enough. The engine wasn't built right.

Factory ring gaps are always correct.
Mitsubishi(and others) use the same ring gap spec for both the N/A AND the turbo models.
That must tell you something?

If it doesn't knock.
Because the knock control actually works.
Then you won't break a piston.
Lots of aftermarket knock control systems don't work.

Bigger ring gaps are really horrible.
More blowby, oil in the cylinder, less octane....more knock.

[digger]

a useful resource for diagnosis of piston failure, there is a download to PDF button the bottom RHS

http://mam.kspg.com/mc/epaper?guid=14c0122387e59c2c

[ProPower engines]

a useful resource for diagnosis of piston failure, there is a download to PDF button the bottom RHS

http://mam.kspg.com/mc/epaper?guid=14c0122387e59c2c

Thanks for posting the link.
I am sure it will come in handy as the wall posters don't cover in detail that the link PDF does

[PackardV8]

a few thou too tight can destroy an engine, especially with hypereutectic pistons.

I'll disagree with that statement. . . . I don't think I've ever broken a piston on an N/A engine. Bigger ring gaps are really horrible.
More blowby, oil in the cylinder, less octane....more knock.

From the United Engine and Machine KB Hypereutectic installation guidelines:

https://www.uempistons.com/installation ... lation.pdf

Modern piston design locates the top ring higher for improved performance. A high top ring operates at higher temperatures and requires a larger top ring end gap. To find the proper ring end gap, multiply your bore size by the ring end gap factor listed on the chart (i.e., Street Naturally Aspirated 4.000” bore x .0065” gap factor = .026” total top ring end gap).

[PackardV8]

Seems I took "non-critical" more literally than the others.
The engines I build most often, the second ring gap is .060 from the start, and they don't stop driving until the top ring breaks and the second ring wears to near nothing. Maybe I misunderstood.
Are military and industrial engines critical or non critical?

.060" from the start, what bore size, what application

cummins, 4.016 bore, first that comes to mind, but quite a few are like that, not just diesels.
Probably they are....trying to prolong th elife of the second ring? I assume, don't know.
Top gaps in the heavy duty stuff are pretty consistent new, but they DO WEAR, unlike a lot of the racing and oe quality modern stuff that barely does.

That's interesting. What about the operating characteristics of modern diesels would suggest a second ring gap more than twice as wide as a heavy duty gasoline fueled engine?

[engineguyBill]

Perfect Circle engineers did some testing on the importance of ring gap on "non-critical" applications several years ago. I don't have the test info in my files today, however the result was that there were no measurable negative results on ring end gaps up to about .040". 4.000" bore size was the test object.
Personally, I feel that checking and file-fitting of the ring gaps is just one of those many things that we, as high performance engine builders, should pay attention to.

What??? 283" Chev. rings installed in a 327" block???? That is just plain idiotic, surprised that the "builder" was even able to get the rings onto the pistons. 0.125" larger bore diameter times 3.14 (pi) would result in a ring gap of at least 0.390". Can't imagine that the engine was even able to start and run with huge gaps and no ring tension . . . . . . . . .

[PackardV8]

Personally, I feel that checking and file-fitting of the ring gaps is just one of those many things that we, as high performance engine builders, should pay attention to.

The difference between something good and something great is attention to detail. Charles R. Swindoll

We are what we repeatedly do. Excellence, then, is not an act, but a habit. Aristotle

continued success is dependent upon tremendous attention to detail. Frederick Lenz

Using best practice every time and then analyzing the result will also result in knowing when there can safely be an exception. My machinist always correctly complains about the analysis, parts chasing and special machine work necessary to build some of the obsolete stuff. However, if all we did was open boxes and assemble SBC383"s, I'd have given it up long ago.