WashingtonRacer

Well I am SOOOOOOO glad I decided to go ahead and replace the whole rotating assembly. So about a month ago I pulled the pan off and found metal all in it. Well from a visual inspection, all looked good, and the engine ran great before that point. Well Today I pulled the pistons out. 3 of them had the top ring broken into a half dozen peices, and 1 of those has about half of the top ring land broken right off. and 1 of the other ones had the oil ring land broken off and the oil ring pushed all out of alignment. A total mess, However I have just done a nail test around the cylinders and they are all still smooth. no visual lines or Hidden lines. I still need to check it in more detail, Everything should be round still with no taper, Since the block probabily has at the most 1000 miles since the last time it was apart.

So the Rings I had were total seal rings. and the pistons were TRW.

Anyone know what would cause the rings and pistons do have this kind of dammage?

Vetterodder

Sounds like you really lucked out! (not about the breakage but that it didn't cause more damage than it did). A few years ago I had ring break on a low mileage rebuild but it only broke in one place, and like in your case, no other damage was done. I have seen rings broken in several places a few times. One case involved a very serious heat problem that resulted from a combination of too tight of piston/wall clearance, inadequate cylinder oiling, and a cooling system problem. Another case involved file-to-fit rings that had been installed out of the box and not clearanced.

In most cases of broken rings, their gap has closed and they continued to expand against themslelves until they snapped. The main purpose of the ring's gap is to allow for growth as they heat. Published specs for gap, typically, allow for expansion in a worse care scenario, including a cooling system failure. I've also seen cases of ring breakage that resulted from piston failure(way too much nitrous and impropery jetted carbs on blown engines). Keep in mind that the melting point of an aluminum piston is well below that of a steel ring.

Monty

Detonation...

Twin_Turbo

Does it look something like this?


Detonation

clem zahrobsky

look at the end gaps on the rings and if they are shiney they were butting each other because the gap was too small. hypereutectic pistons require special end gap on the rings. :chevy

CFI-EFI

Detonation was my first thought, too. Also, where is the gapless ring installed? Actually Total Seal sells rings other than the gapless, so I am making an assumption, here. If the top ring is a conventional design and if it had insufficent gap OR became way over heated, the ends of the ring can butt against each other with enough force, for the ring to get stuck in the bore and pull the top land out of the piston on the down stroke. This would be another explaination for the piston damage other than detonation. Of course, it could be a combination of the two. It sounds like you got lucky on cylinder damage. Double check the recommended clearences for the components you're using and triple check YOUR clearences for complience. If this IS a racer (WashingonRacer), looser is better(to a point). Good luck and...

RACE ON!!!

WashingtonRacer

Hmm.. I know detionation would cause something along these lines, but wouldn't you see excessive heat scoring?.. On the other hand. I never experienced much detionation. I am going to jump to the assumption that it was caused by incorrect end gap. I built this engine in my seinor year in high school. On top of that It was my first time even building an engine. I Never thought of the seriousness of the propert gaping of the rings. All I did was match the new rings up to the old ones. even then I was not that careful.
The Gapless rings are the the second landing. "comprssion ring correct?" and those were all just fine. I really like the design of those gapless rings. they allow you to run a rather large gap yet still you can have the effects of one with no gap at all. Why don't they do the same for the top ring?

WashingtonRacer

Oh, and Twin turbo. Is that the piston face missing? WOW that is pretty messed. but no mine are all on the rings and grooves that are broken. I really need to go get a Digital camera.

Twin_Turbo

Yup, it's the top ring land & part of the crown, comepletely broken away.

CFI-EFI

Typically, Yes. There have been problems designing a gapless ring for the top groove. But there has been a recent release of a gapless TOP ring. The reason I asked which groove YOUR gapless rings were in, is because of the recent release and that your failure was more typical of a top ring failure.

RACE ON!!!

arnold

Ya, TS's top gapless ring has been out and about for between a year and two.
If indeed the ring gaps did butt, really surprised no visual wall scoring was noted. BTW, gapless 2nd ring traps compression pressure between top and 2nd ring, upsetting top ring seal. This makes the top gapless ring a more sound choice. Another BTW, to alleviate the possibility of trapped pressure between top and 2nd ring, Sealed Power recommends a 2nd ring gap larger than the top ring.

gkull

I've only owned one motor with gapless rings. I've since used high quality ones that come with the master racing kits.

What I really wanted to say is: That I intended to install a high hp NOS system so I installed JE blower pistons which are much thicker above the first ring.

jackson

Clem:
:confused: Would you shed some light on why hyper pistons require special ring end gaps? I've never heard that before and conflicts with a quote from Speed-Pro publication X-3009: "Our hypereutectic pistons operate perfectly with standard ring end gaps, and have conventional ring land locations." Perhaps S-P info is obsolete & yours is more current ... dunno? :confused:

danno85

The ring end gap requirement has nothing to do with what the piston is made
out of, but rather how much heat the ring gets and therefore how much they'll
expand. The KB hypereutectic pistons have a high ring placement, which means the ring will get hotter and expand more, so it needs more gap. According to your quote from the SP bulliten they're running a conventional
ring land location and so a standard ring gap is adequate - makes sense.

Dan

jackson

With clarification of higher ring pak ... as opposed to material ... makes perfect sense. Thanks.