Head/Piston Damage Continued

[Jdddrigot]

About a month ago I posted pictures of head/piston damage on My 1975 02A. Well, the culprit has been found. Now I’m desperately searching for at least one stock piston with the lowest piano top (89mm). The mechanic would like an entire set but I really only need one. I will post in WTB too but thought I should try this as well. Plus I figured everyone would enjoy the pictures. Yes, it was cylinder #2.   Amazingly the walls were clean. 

[2002Scoob]

So what was the Culprit? 

 

Still not clear to me. Yah, those ring-lands are toasted.... but why, and what else caused all that damage?

 

Unless you're just lookin' to get out from under the car/motor (bad karma IMO), or wanna just run it till you can afford a bigger, better build(EV SWAP?!?!)

 

I'd vote to follow your mechanic's suggestion, get a matching set of decent pistons in a slightly hotter compression ratio than stock if ya can afford it, and get the machining done on the block to match the piston set ya end up with. You'll be happier in the end.  

 

Just me

BTW, thanks for the photos! I think we all are gluttons for carnage, and I love that you're taking it in stride. We've all been there! (or very likely will be at some point)

Edited May 5, 2021 by 2002Scoob

[Jdddrigot]

1 hour ago, 2002Scoob said:

So what was the Culprit? 

 

Still not clear to me. Yah, those ring-lands are toasted.... but why, and what else caused all that damage?

 

Unless you're just lookin' to get out from under the car/motor (bad karma IMO), or wanna just run it till you can afford a bigger, better build(EV SWAP?!?!)

 

I'd vote to follow your mechanic's suggestion, get a matching set of decent pistons in a slightly hotter compression ratio than stock if ya can afford it, and get the machining done on the block to match the piston set ya end up with. You'll be happier in the end.  

 

Just me

BTW, thanks for the photos! I think we all are gluttons for carnage, and I love that you're taking it in stride. We've all been there! (or very likely will be at some point)

The mechanic thinks the car overheated because of low coolant causing the rings to disintegrate. I had checked the coolant and always watched the temperature gauge and both seemed fine for April in Colorado. 
 

The car is enough of a go-kart for me so I’m planning on staying with the 8.3:1 compression unless I don’t have a choice. I did find a used set on Fleabay so that may be the route to go. 

And no EV swap for me. I’ve already had a Leaf and an Audi E3 Etron. Fun but I’m kinda liking the utter simplicity of the 02. 
 

More good news - last night our financial advisor said to keep it unless the expenses stay high. I do think I’m done buying so that just might work. 

[2002Scoob]

That's a mighty clean looking engine bay. Hold onto her!!!!

 

It's weird you have a financial advisor regarding your vehicles, unless it's your significant other. Which makes perfect sense, honestly, haha. BTW... there ain't nothin' simpler than a single gear, clutch-less drivetrain with just a few moving parts vs. a few hundred.... But that's just me. 

 

It's Mexican day, and while I live in Germany I'm half-zies. And also 3 Mezcal Margaritas deep, so I apologise for nothing. Please refer to everybody more knowledgeable than I. Thats most everybody.  Salud!!!

 

 

 

[jimk]

1 hour ago, 2002Scoob said:

Still not clear to me. Yah, those ring-lands are toasted.... but why, and what else caused all that damage?

High miles?

Saw this before on high miles $50 engine bought for parts.

[2002Scoob]

12 minutes ago, 2002Scoob said:

Please refer to everybody more knowledgeable than I. Thats most everybody.  Salud!!!

 Speaking of... @jimk 

[tech71]

3 hours ago, Jdddrigot said:

Now I’m desperately searching for at least one stock piston with the lowest piano top (89mm). 

Beware! You are now standing at the lip of the dreaded "Mission Creep Vortex" Also know as the Rabbit Hole.

One false step and next thing you know, your engine is at the machine shop being bored and fitted with new pistons. Cant leave those floppy timing chains now, seems a shame not to look at the oil pump,

Yaaugggh! Your trapped in the Vortex?

 

 

[Son of Marty]

Be sure to reinforce the drivers side engine mount if it hasn't been done already.

 

[TobyB]

Soooo...

 

one of the things that happens is, the ring lands wear, and wear, and wear.

This causes the rings to twist more and more.

 

Eventually, they can't take the twisting, and break.

 

Once they break, the ends go to work on the lands for realz,

and the ring- chunks make a bid for freedom.

Through the crown of the piston.

 

I did that once.

 

Head didn't look quite that bad, but it was the same idea.

 

t

 

[jimk]

With the dings on the head in more than one cylinder, it will need more than one piston, like 4 maybe.

[Son of Marty]

Any used m10/m30 piston needs to have the ring grooves inspected and measured closely, that's where most of them wear out first. 

[Mike Self]

Some years ago I had a Renault engine with a piston whose ring lands looked exactly like yours--except no pieces broke off the top ring and made its way into the combustion chamber.  The ring just kept flopping back and forth until it was nearly worn to a point at the gap.  Amazingly, that cylinder's compression was only a few lbs lower than the other three, and there was no damage to the head at all.  And it didn't burn much oil, either--4 ring pistons and the oil control ring was undamaged.

 

If you're gonna keep the car--and if the engine room's cleanliness is any indication, it's a nice one--dive head-first into that rabbit hole and do the engine correctly--and it'll be good for another 200k miles.

 

mike

[Solarphil]

18 hours ago, Jdddrigot said:

The mechanic would like an entire set but I really only need one. 

 

 

 

Listen to your mechanic.  There are some things that really need to be matched in sets, and pistons are one of those things. I know you’re thinking only one is damaged so only one needs to be replaced, but trying to do that will likely cost you far, far more in the long run.

 

Besides, for someone selling a set, like the guy in the classifieds with the grand piano tops, breaking up the set would leave him with three expensive paperweights.  Not a lot of Geo Metro tuners out there looking to upgrade to M10 pistons ?

[Conserv]

Given the condition of (a.) the head — trashed, and not just combustion chamber #2 — and (b.) your #2 piston, I find it hard to believe that your engine’s other three pistons aren’t also close to failure. If your mechanic is charging you little or nothing to remove your car’s engine, open it up, drop in a single replacement piston, re-assemble the engine, re-install the engine, and get the engine running decently, go ahead. Otherwise, I think you’re throwing money into a hole with your “replace-one-piston” approach, and you’ll be paying your mechanic to do the same thing in a thousand or two miles, when the next piston fails. And again when the third piston fails. And, again....

 

At a bare minimum, listen to your mechanic’s recommendations.

 

My honest opinion!

 

Regards,

 

Steve

 

[Jdddrigot]

24 minutes ago, Conserv said:

Given the condition of (a.) the head — trashed, and not just combustion chamber #2 — and (b.) your #2 piston, I find it hard to believe that your engine’s other three pistons aren’t also close to failure. If your mechanic is charging you little or nothing to remove your car’s engine, open it up, drop in a single replacement piston, re-assemble the engine, re-install the engine, and get the engine running decently, go ahead. Otherwise, I think you’re throwing money into a hole with your “replace-one-piston” approach, and you’ll be paying your mechanic to do the same thing in a thousand or two miles, when the next piston fails. And again when the third piston fails. And, again....

 

At a bare minimum, listen to your mechanic’s recommendations.

 

My honest opinion!

 

Regards,

 

Steve

 

Thanks Steve. I do appreciate an opinion more informed than mine. Right now I’m only finding used pistons in the correct bore on Ebay. Would you install used with new rings?  What are my other options?  Kinda how I’m feeling at the moment -