Rings have moved

[mag2555]

And how does the Moly face band on each compression ring look, scratched and beat up?

Also it would not be the first time that a set of second compression rings where mis stamped as to which way they should face, so you could be scraping oil up into the chamber!

[kimosabi]

Four strokes have the rings turning. 2 strokes you dont want them to turn, hence why the 2 stroke pistons have a locating pin.

[engineguyBill]

Yes, piston rings do move a substantial amount as the engine is running. Top ring, second ring and oil ring assembly all rotate at different speed due to the differences in face design, materials, tension, etc. Crosshatch pattern will not result in abnormal oil consumption, nor excessive leakdown.

1. The Hastings ring set probably uses a reverse-twist, tapered face second ring. Make sure that these rings are installed correctly. If they are installed upside-down, they will actually pump oil up into the cylinder.
2. Check the oil ring rails and expanders, make sure that they are installed correctly.

Are you using used pistons? If so, check the ring grooves for excessive wear also check the cylinders to make sure that they are round, with NO taper.

[piston guy]

thumpernz,
It's pretty tough to have 18% leak down on a 5/64th compression ring in that short of time. Check the ring orientation as Bill suggested. I got a call a few months back for a nice gentleman back east. He claimed the was an oiling problem with a set of pistons and felt it was the piston's fault. I suggested he send them to me for inspection . He balked saying at '67 he was probably old enough to be my dad and had assembled more engines than I'd ever seen but he obliged. Upon receipt and inspection I found EVERY second ring installed upside down and the absolute reason for the oiling. When I got him on the phone I mentioned what he had done followed by "At '65 I'm old enough to be your younger brother and if I was standing next to you right now I'd be slapping the back of your head!" Point is don't overlook anything , because if you do , some smarta$$ may point it out to you!
I hope you fix it with the new ring set. Best of luck.

[ThumperNZ]

Yes, piston rings do move a substantial amount as the engine is running. Top ring, second ring and oil ring assembly all rotate at different speed due to the differences in face design, materials, tension, etc. Crosshatch pattern will not result in abnormal oil consumption, nor excessive leakdown.

1. The Hastings ring set probably uses a reverse-twist, tapered face second ring. Make sure that these rings are installed correctly. If they are installed upside-down, they will actually pump oil up into the cylinder.
2. Check the oil ring rails and expanders, make sure that they are installed correctly.

Are you using used pistons? If so, check the ring grooves for excessive wear also check the cylinders to make sure that they are round, with NO taper.

Just checked the piston rings, and definitely the 2nd ring has the contact edge down and the spot on top.
Expanders are all butting and are freely able to move.
One thing I have noticed is the PCV valve seems to not seal that well, so could have been sucking oil as well as causing a lean condition. I'll replace it regardless.

[user-23911]

PCV valves don't have to seal.

Only when used with boost.
Those ones are different or SHOULD be different.

[sprint40]

"the free gap is about 3/16" less than a new ring" You just found your problem with that quote.

[mag2555]

Be sure you also do not have excessive back clearance with those compression rings , they should beable to sneak into the groove by no more then .005" .

[Dave Koehler]

Throwing out a monkey wrench here.
Ever take a good sealing engine apart but looked close at the rings just before they exit the cylinder.
You see the top ring location, bump a little more out to see the second ring location.
The second ring gap may be close to the top ring gap location but not in line.
Take it the rest of the way out and poof, due to the relaxed rings they now appear to be lined up.

[jsgarage]

On teardown of an old 327 Chev commuter before rebuilding, all the top two cast iron rings were worn into T-shapes all the way around, in stock cast aluminum piston lands. I'm still not sure how such a thing could happen but for sure, the rings were not just moving but spinning in their grooves.

[wjnielsen]

I understand that the rings move in operation, but I have a dumb question:

Why is it important to orient them a certain way on the initial build if they are just going to walk around the piston anyway?

Winner winner chicken dinner!

I've always thought that any possible benefit was that the tiny (microscopic?) little 'streak' of oil that *may* sneak up thru the gap in one ring gets caught by the subsequent ring?

As far as the gaps lining up, I would expect that if it were to actually have an effect, it would be to reduce ring flutter due to pressure between the top and second rings...

[BrazilianZ28Camaro]

Check the cylinders for ovality.

The rings might not rotate if the bore is oval, being stuck due its natural tension against the cylinder bigger size diameter.

Also some Speed pro instructions are pretty damn confuse regarding top/second ring position. Worth a check IMHO.

Good luck.

[Tuner]

Check the cylinders for ovality.

The rings might not rotate if the bore is oval, being stuck due its natural tension against the cylinder bigger size diameter.

Also some Speed pro instructions are pretty damn confuse regarding top/second ring position. Worth a check IMHO.

Good luck.

There's your clue, boys. ^^^^

The side thrust resulting from rod angularity causes the cylinders to distort to oval shape and the rings conform to minimum friction.

In a time too long ago I ran a 454 BBC in a flatbottom boat towing speed skiers. The iron open chamber 12/1 ZL-1 cam crate engine I was fortunate to have had a lifter bore askew and ate a 6 camshafts in the course of a season's racing (which GM warrantied, thank you to my pals at the Chevy dealer and the GM warranty guy who gave us another long block for the next season). I tore it down to wash the iron dust out of it each time. Each race session might have several minutes of running WOT at 6000 to 7000 RPM (RPM dependent on skier enthusiasm, water conditions and cavitation plate position) and at least an hour of 5000+.

Every time I assembled it with the gaps in position as per the GM service manual. Every time I tore it down the rings were lined up and every gap was in line 90* to the crankshaft axis, top of the cylinders on one side and bottom on the other. What I don't remember (rats) is which direction, with or opposite crank rotation.

Every cam change and cleanup included a polish job on the cylinder walls with the 400 wet-or-dry with a trickle of water method, so that probably caused it LOL.

[ThumperNZ]

Besides the rings having lost tension, I think I found another cause for the "smoking on the RH bank".
I just completed installing the rotating assembly, so I thought just by chance that I would check the full mark on the oil dipstick. It was within 3/16" of the bottoms of the rod bolts, (this engine has Eagle I beam rods). I thought that's strange so i checked the length against stock 283 SBC dip sticks and tubes, the net difference was 7/8" less than 3 other dipsticks & tubes. It seems that after delivery, the shop that I delivered the engine to, broke the dipstick, so they welded it, but forgot to allow for the broken amount. 7/8" on the 45 deg is equal to 5/8" vertical, so its sure that they were running the oil level 5/8" closer to the reciprocating assembly. My theory is that the oil bunches off the crank, then gets into the crankcase oil level and flings it against the RH bores. I'll bet if the oil was drained by 1-1/2 qts the smoking would have stopped, but I guess the damage to the rings was already done by then. All the bores are perfectly round and scuff free, engine is about ready to deliver again, this time stern words to be issued.

[mag2555]

Nice find, it's good that you dug deeper !