Munched Piston (PICS) - What the hell caused this?

[stradlater]

Here's the pics of the pistons out of my now defunct 1g. I have dismantled one of the pistons completely, the worst one, and taken up close photos of it. The rest of the pics are of the other pistons, which are in varying condition.

One question though, how the hell are you supposed to get the rings on and off? I took the rings off the dead piston, and I've managed to scratch the sides a bit, how do I avoid doing that?

Anyway, check these out..
What do you think caused this?








There's a lot of carbon build-up around the pin. What causes that?

Clearly Toyota's Engineers view there work as more artistic than scientific???



What causes the scraping at the sides? Will this have affected the bores?

[stradlater]

The rings. I don't think they're dead? They look ok?



Other pistons have similar dints on them, but there aren't as many on each piston.. Does this mean that the pistons are useless if they have these dints?

[oldcorollas]

ever had a bit of the spark plug centre electrode insulator come off? it does things liek that...
basically it's eaten something, bounced it aorund a bit and spat it out.. (and happens where there is squish area in the head...)
are there similar marks in the head?
if not, the head may hav ebeen repaired/replaced

ART is the manufacturer that makes them for toyota...

[stradlater]

I figured as much RE: the ART thing, but I thought it was funny all the same.. Clearly they aren't forged either, as you can see the casting bits.

As for the head, there are marks, but not necessarily corresponding marks...

The insulator did come off the electrode of one of the plugs, all gone all together. That may have been that piston hey.

But are any of those things detonation marks? They don't look like it to me. Looks far more like the engine has eaten something, but in so many cylinders???

Also, how soft is the piston metal? Is it possible to dint them just while loosely transporting them more working on them?

[oldcorollas]

not dint them that much (on top).. you'd need to give them some pretty solid whacks with sharpened hammer
it is also (apparently) possible for bits to be spat back up the intake, and go into other cylinders, before going out the exhaust valve.
or it might be from unrelated bits of stuff being eaten (but there is not much that should be coming off in there)

no idea re detonation. the sharp dints are from solid object hitting with large force, or being trapped between squish area and piston... usually...

any ceramic left in the bottom of the dints? how many dints are there? perhaps it could be less than 20 impacts = 0.2 seconds at 6000rpm

piston to bore clearance not right? pistons wobbling around?

[stradlater]

Fuck, could be all of those things really...

Although, the head gasket o-rings were properly fucked, so it could have been the piston colliding with that.

[Aust162]

If the head looks "pitted" around the valves/spark plug thread, that's usually is detonation.

The rings may look OK by eye but without sitting them in the bores and testing the ring gap, then you just dont know.

[mrshin]

You take rings on/off with a ring expander, of which there are a few sorts - some of which are similiar to circlip pliers.

As for bore condition, the best thing to do is have a look at them. If you're not sure what to look for, get someone who's rebuilt a few engines to have a look, measure them, etc.

[stradlater]

I'm not actually going to be using these bores anyway, so I'm not too concerned, I'm just interested in seeing why these pistons are so buggered up...

[mrshin]

Take some pics of the bores, and how old was the bottom half of the 1G anyway?

Next time be sure to pay some careful attention to tuning... Having said that, there are many engines with much more damage than yours.

[GasedT18]

stradlater,

apart from spark plug ceramic and turbo blades is there a possibility that somene put a screwdriver down the spark plug hole to check the position of the piston for timing purposes and it's jammed? Else someone has been a bit sloppy around the workshop and they've been dinged up.

And what does the bore look like where that one piston has wear marks? Either the piston has gone out of round or the bore has or something has lodged down the side or there is some slack in a bearing fit and some funny vibration/ignition thing is allowing the piston to slap the bore. When bores wear a lip of metal remains at the top of the bore but I would expect the piston to miss it.

The staining is from oil coming out from the pin.

Rings are taken off and put on with ring pliers.

I don't think the damage is serious.

My 2c

D

[stradlater]

Hrm, fair call.. Seems something very bad has hammered the top of these pistons, because there's marks such as those on all the pistons, just not as bad.

W.R.T. the damage not being that bad, Um, that piston isn't usable anymore though, I sure as hell won't be using it again. Question is, for the pistons where the damage is a lot smaller, is it possible grind the holes off?

[oldcorollas]

oh, as for the side scuffing at the top...

what happens when you get a signle piece of very incompressible ceramic, and try to compress it between piston and head, on one side? the piston is tilted in the bore, cos that side doesnt go up anymore (at least not as much)... i reckon the small scuffing at the top is from that...

also, the sides of the piston have been peened as such, by impacts, pushing material out to hit the bore, which could affect the position of piston in the bore....

i can do a dodgy MSpaint if that helps?

[stradlater]

No no, I think I've got the idea of what your saying.

In short, something has come very badly adrift in this engine...

I suspect insulator and bits of the head gasket when it's fallen to bits.

But these dints look old? as in they're been there for a while? The insulator only came off in the last 10 minutes of the engines life, at best!

Well, I'm gonna pull my other engine apart.

What's the best way to get the pin circlips out?
I've got a set of needle nose pliers, but they dont' appear to be needle nosed enough..

[stradlater]

Just noticed that in two of the dents, on different pistons, bits of a white material, actually embedded in the top of the piston..