#6 Piston Damage w/Pics (1 Viewer)

[Tools R Us]

Bring it back to TDC, pick, remove any porcelain, sand off anything sticking up. I would not attempt to remove the dents, they will be filled with carbon pretty quick.

 

[bigredmachine]

Tools-R-US: When you say remove, do you mean remove the piston or just the surface pitting? Any recommended grit or grinding tool to smooth things out?

BRM: Sorry, need a little help with the cross-hatching. What exactly does it look like?

AJP: I plan to do the valve guide seals, etc. I have not cleaned the valves up enough to inspect them for pitting.

Spike: Too late. Already turned it. Can you turn the engine over counterclockwise?

cylinder crosshatch‏ - بحث Google‏:
that is a picture of cross hatching, it should still be visible on the cyl walls

 

[AJP]

Tools-R-US: When you say remove, do you mean remove the piston or just the surface pitting? Any recommended grit or grinding tool to smooth things out?

BRM: Sorry, need a little help with the cross-hatching. What exactly does it look like?

AJP: I plan to do the valve guide seals, etc. I have not cleaned the valves up enough to inspect them for pitting.

Spike: Too late. Already turned it. Can you turn the engine over counterclockwise?

actually ... wasnt really thinking about the face of the valves as much as the seating edges, the seats themselves, stems and guides; a chip from a valve guide could also cause that damage as well as break the plug porcelain .... and could cause scoring on the way out past the exhaust valves, guides etc. While it certainly looks like all of the problem was from the plug debris ... I would still keep an open mind about this till you are certain nothing else started a ‘chain’ reaction. A long shot but worth checking everything carefully.

 

[BILT4ME]

What's the bottom of the HEAD look like? It had to get mashed between SOMETHING when doing it.

If you REMOVE material from the piston, then you are changing the weight of THAT piston and thus, making the rotating assembly out of balance. Kind of a damned if you do, damned if you don't situation.

 

[scottryana]

Yeah but smoothing that out you’re not talking about much maybe a gram to a gram and a half. For visualization a paper clip weighs about a gram. You would be lucky if your factory balance is that close. I wouldn’t worry too much about that, but those sharp edges do have to be taken off they are hot spots for detonation.

What's the bottom of the HEAD look like? It had to get mashed between SOMETHING when doing it.

If you REMOVE material from the piston, then you are changing the weight of THAT piston and thus, making the rotating assembly out of balance. Kind of a damned if you do, damned if you don't situation.

 

[medikateme]

Cross-hatching is present but nearly as distinct as it is in the other cylinders. Also included are picks of the underside of the head. I appreciate the input so far. Thank you.

 

[AJP]

It would be interesting to see the exhaust valve seats

 

[gummycarbs]

Welp, now I have a new thing to have nightmares about. I've never seen an insulator come apart like that.

 

[scottryana]

I have. But like I said earlier I think we are looking at a chicken before the egg, or vice versa situation here. When the spark plugs come apart it is usually from detonation. Then you have sharp spots on the piston/head that cause detonation. So I would look very closely at the wiring to the injector, and the injector itself to make sure that, that cylinder didn't some how run lean.

Welp, now I have a new thing to have nightmares about. I've never seen an insulator come apart like that.

 

[medikateme]

Not sure if this what a few of you were looking for. Let me know if you need greater detail. Pics are of the #6 injector and plug and the valve guides for the #6 cylinder both exhaust and intake.

 

[medikateme]

Also the plug wire.

 

[scottryana]

Can't really tell much by the pictures you're going to have to get the injectors tested and cleaned anyway.

 

[medikateme]

All the injector connectors were crispy. #6 was wet on the exterior. May have been the valve cover leak.

 

[FJ40Jim]

Injectors can't be judged too much on appearance.
But the valve seats... ouch. Definitely need a good valve job on that head. The question is will the seats need cut too much?

 

[FJP971]

My question is how were all of those gouges created in such an isolated area of the cylinder? Could they have been caused by the spark plug insulation breaking off, falling in, and being crushed a couple of times before they flew out the exhaust? Is the aluminum that soft that ceramic insulation could cause that kind of gauging? Strange if you ask me.

 

[medikateme]

FJJim: What is it about those valve seats that catches your attention? First rodeo for me here.

FJP971: Could not find any remnants of porcelain. Machine shop guy said he's seen it before. Usually with vehicles that have gone 70-80k miles without having the plugs changed. Didn't seem phased by it. Said he can clean up the head. Any thoughts on what may have caused it?

 

[flintknapper]

FJJim: Any thoughts on what may have caused it?

No telling. Part of the spark plug, something someone dropped in the intake, who knows.

Doesn't look like it spent much time in the cylinder before exiting the exhaust port.

 

[steveLX450]

I would suspect it was initially caused from detonation “preignition”, then spark plug failure, possibly from tight exhaust valve clearance or lean air fuel mixture. Looks like a Denso spark plug ? Was it the correct heat range ? How many miles on them ? I dont think the spark plug failed due to age / miles. Post some pictures of the thrust surface side of the cylinder wall on the exhaust side as that looks like where the damage is on the piston. I would bet the piston skirt is scored from metal transfer. Looks like a full rebuild.

 

[Tools R Us]

FJJim: What is it about those valve seats that catches your attention? First rodeo for me here.

FJP971: Could not find any remnants of porcelain. Machine shop guy said he's seen it before. Usually with vehicles that have gone 70-80k miles without having the plugs changed. Didn't seem phased by it. Said he can clean up the head. Any thoughts on what may have caused it?

I'm with the machine shop guy, rare but have seen it before. Maybe a defective plug, could have been dropped before it was installed? If a plug has a crack, this type of thing can happen. The porcelain is relatively light, so went out the exhaust.

 

[Michael Hanson]

Hi, I've seen it due to engine running too lean and also water entering the combustion chamber. If the center of the plug gets too hot it expands and breaks the porcelain . Dirty engines and poor valve train can create all kinds of problems. Mike