Anyone know what happened to this piston/cylinder??

[sutor623]

Hey guys, just wondering what was the cause here. Cyl. #1, V4 looper 90 degree. Possible detonation? Funny thing is that this is the only piston that looks like this. This is aluminum jammed into the piston crown. I do know that the motor was overheated at one point in its life.









Obviously the debris made its way between the piston and cylinder walls:




What's up with the recess in this ring? This is strange to me. It is on the exhaust side of the piston.







Debris in the intake port. This did not come from the crankcase as far as I can tell.........

 

[alldodge]

Kind of looks like the needle bearings in the crank are being sucked through

 

[GA_Boater]

Is the stuff in the intake port magnetic, sutor?

 

[emdsapmgr]

An overheated engine winds up running "lean" when it's super hot. That lack of lubrication might result in the piston rings scrubbing the side of the cylinder walls. You can see the vertical gouges. Esp, the rings seem to be rubbing against the top of the port openings. Any chance this piston was replaced at some point? If the block was bored at some point, was the block washed correctly after machining-to get rid of the small machining debris? Is this piston a factory piston, same part number as the other 3?

 

[fhhuber]

The engine ingested a piece (or a few bits...) of metal... exactly what that metal was... could be almost anything, including a screw from the carb butterfly.

It rattled inside the cylinder a bit... maybe got cut up between exh port and piston/ring (lucky no broken ring that I see...) and generally did your cylinder & piston no good.

I've seen that type damage from a carb butterfly screw in a lawnmower engine.

You need to find all the bits of metal that may not have exited the engine.

 

[sutor623]

Well, since I couldnt figure out what was going on, I just got a reman powerhead. But I still want to know what went wrong here.

I will see if those shavings are magnetic.GA. EMD I will take a look at part numbers, but I am 99% sure this is the original, factory build.

I am still wondering though, what in the world happened to that upper piston ring? I have never seen the middle "missing" like that before. Very strange. And this cylinder passed a leakdown and compression test....................

 

[fhhuber]

Somehow... I didn't see the bad ring till pointed out. I was probably busy looking at all of the other stuff that was going on.

Inadequate oil and the ring catches the edge of the exhaust or intake port will shear the ring like that...

Or a bit of metal ingested trapped between piston and cylinder at the port can cause the ring to fail.

Then you have bits of ring (and probably whatever it ingested in the first place) floating around and spreading the damage.

The edge of the port isn't chamfered and that helps the ring catch, but something else had to happen to make the ring shift into the port.

Looks like its a probably a rebuildable core.

I'd still bet it ate a screw or something as the start of the failure.

 

[GA_Boater]

I asked about magnetic cuz that could be the ring remnants.

That isn't a normal broken ring,

 

[Faztbullet]

I don't see any pic's for some reason but it sounds like the locating pin in piston migrated out...this will cause the the indentations and if stuck in head preignition resulting in aluminum throw off. Then the ring will rotate and hang in exhaust port and break..

 

[sutor623]

I asked about magnetic cuz that could be the ring remnants.

That isn't a normal broken ring,

I know, it is very strange isnt it? The odd thing is that the top and bottom aspects of the ring measure the same as if the indentation was not present. I almost think that this ring was bad from day one. Doesnt make sense how the upper and lower edges wouldn't be rounded off or deteriorated with the rest of the ring.

I guess step one, like you said would be to see if the metal particles are magnetic. I, for some reason think they are aluminum. What are the rings made of, some sort of steel I am guessing?

 

[sutor623]

Oh and just to be clear, motor ran very strong at cruise and upper rpms bands. Idled solid when it wanted to.

It was really hard to start when cold, had some surges of rpms at initial idle, and failed the drop test for cylinder 1 miserably at idle. Also failed cylinder 3, but not nearly as bad. The motor would run on cylinders 2 & 4 at idle in the driveway, but if you pulled either 2 or 4 with all the other cylinders running, the motor would die out. Basically, this motor was running well on 2 cylinders.

And to make it more frustrating and difficult to figure out, compression was even across the board.

I also believe the head gasket was bad and letting water into cyl 1 and 3. (Probably after the overheat, which I only know happened because the thermostat poppet was melted when I replaced it.)

 

[emdsapmgr]

Fast brings up a solid point. Did the locating pins come out of the failed piston. If so, the ring can migrate around the piston, to the point where the ring end might hang up on one of the ports, causing a chafing affect-and metal chips. Do the locating pins seem to still be properly located in all the pistons?

 

[sutor623]

Fast brings up a solid point. Did the locating pins come out of the failed piston. If so, the ring can migrate around the piston, to the point where the ring end might hang up on one of the ports, causing a chafing affect-and metal chips. Do the locating pins seem to still be properly located in all the pistons?

Yea, all of the locating pins are in their proper places. Man, if one of those came loose it would be catastrophic!!!!

 

[racerone]

In the 1960's they promoted ---" molybdenum filled " rings said to have a low co-efficient of friction.---And I know that this motor is newer here.

 

[emdsapmgr]

Anytime you suffer a powerhead failure, you need to determine the failure root cause. Usually that will include a teardown and autopsy on the carb that feed that bad cyl. Was there any restriction/debris inside the carb jets which may have restricted fuel flow to that cyl? Causing it to run lean?

 

[Faztbullet]

This engine has been running high temps as sleeve has turned. The ring is worn like that due to ring flutter from excessive clearance in ring groove and the little dimples are stamped into piston and either are EXT or STD if cleaned off.

 

[sutor623]

Anytime you suffer a powerhead failure, you need to determine the failure root cause. Usually that will include a teardown and autopsy on the carb that feed that bad cyl. Was there any restriction/debris inside the carb jets which may have restricted fuel flow to that cyl? Causing it to run lean?

No, no fuel restriction, but cylinder 1 had damage, and cylinder 3 had some, albeit minor, as well. The thermostat grommet in that head was completely melted to where water would just pass by it freely. I am sure there was an overheat, probably at idle.

 

[sutor623]

So, to answer some of your questions, the debris that was in the intake ports was NOT magnetic. I guess it could be from the piston itself? It is definitely not ring debris.

Also noticed something odd, and very irritating. I believe that the factory installed a BAD ring from the get go. Because, the depression in the ring is also noticeable in a different spot, that I failed to notice.

Here is the main area:



And area I just noticed:

 

[sutor623]

This engine has been running high temps as sleeve has turned. The ring is worn like that due to ring flutter from excessive clearance in ring groove and the little dimples are stamped into piston and either are EXT or STD if cleaned off.

Just noticed this. So that sleeve is in fact turned? Does it need to be resleeved or can it be turned back? What is ring flutter exactly? Excessive movement of the ring maybe?

 

[emdsapmgr]

I apologize to Fast for not picking up on the fact that the sleeve has turned inside the crankcase. That's an astute observation, and is critical to understanding what's going on inside the block. A spun sleeve can change the orientation enough that the ringset end tips can catch part of a port, starting to shave metal. It can also start to catch the ring on a lip of a port. Certainly you've got a defective ring, just not sure if it's as a result of the spun sleeve. Something hard caused the groove on the piston skirt and ring groove. Spun cylinder liners are extremely rare, but do happen. Once the liner spins, it starts to close off the intake exhaust port air/fuel/exhaust flow and the two cyls on that side will start to go down on hp. When you go looking for why it's down on hp, usually it's the odd compression numbers that lead to examination (pull the head) and then find a spun liner. New blocks are warrantied for this type event. The rest are scrap. I wouldn't put a new liner in this block.