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

[jeffro ra28]

ok, so looking at the photo's. Where has the molten aluminium come from? Has it been pulled out of the pistons then bashed straight back into where it came from? And wouldnt the molten aluminium form in a ball shape and not a sharp shape?

[stradlater]

Jeffro: Agreeing with you mate... It's something that the engine has ingested. Just not sure what. Not sure about your thoughts on the bearings though. When I said silver, I simply meant they looked metal coloured.. I'll be using King bearings, as I know they'll work and fit, and I'll be using new rings but standard (albeit in better condition) pistons.

TheChuckster: Dunno mate, makes sense to look though. In reality the engine could have ingested a lot of things i suppose, but the gas carbi has a rather large venturi setup that would prevent anything big from getting in there.. The carbi itself actually wasn't oily, but it did have coolant all through it thanks to the head gasket.

Terryo: Not sure I can agree with you on that one mate. I can't see where the balls of alloy have come out of, as there's no marks on the pistons that are 'smooth' everything is sharp edged. I've no doubt that this engine detonated at some point, but it hasn't been doing it regularly, and I just can't find any spots where that sort of metal would have gone through the engine like you said.

I'm beginning to think, given that everything else is find, this engine has had the damage for ages, prior to me getting it.

[AndyTTR]

Could the white stuff in the dents be bits of insulator from the plugs? It smashed all the plugs just before it died didn't it?

[stradlater]

No, it only smashed one plug, atleast one plug INSIDE the engine...

But yes, I'd agree that the white stuff is insulator.

[MS-75]

I'm beginning to think, given that everything else is find, this engine has had the damage for ages, prior to me getting it.

Odds-on I reckon.

That's FOD.

[twentyEight]

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

Not sure what would have caused it, but there was scraping on some of your bores also, and it was about the same amount of wear on the piston as shown in the above pic...

[stradlater]

There was scraping on the bores? I didn't see that? Where?

MS75 - FOD???

[twentyEight]

From memory, bore 1, and a couple of others may have also...

[stradlater]

Ah well, I'll be getting new bores anyway..

[MS-75]

Foreign Object Damage (FOD)

Abbreviation I still use from my days at Qantas.

[stradlater]

FOD.. Haha. FOD indeed. Cept I'll bet it wasn't a bird, like it would be on a plane.

[kickn5k]

As all pistons are well now are cam ground or turned the "stained" area is were the piston has most of its clearance (normally .020"), and the bore having so much clearace it wont scrap off, normal for a full skirt piston. The suffing (top ring land) can also be from combustion being to lean or engine running hot exactlly as bored said.
Forged pistons would be the go. But in saying that everthing will go bang if it detonates

stu.

[stradlater]

Forged pistons you say??

Selling a kidney you say???

[AndyTTR]

Can you apply for a government grant? You know, for the promotion of renewable energy that you're doin with the LPG?

[stradlater]

I'm gonna try.. Hehe.