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[GastronomicKleptomaniac]

...after pulling the front of the engine to bits, found the timing was still right, so moved my attention to the top. Found a bolt missing from a cam cover (!?), a nice oil mist over the rear of the engine, but no oil in the plug wells, when I'd took the coil pack off.
 So, after about 10 hours of careful disassembly (rather do it slow and well...), I got to the plugs - front pass side showed signs of overfuelling, but still didn't account for the noise... pulled the middle plug out (cyl. 4?) - and found it had sheared off, so the electrode end was bouncing around the combustion chamber...

 So, I'm officially saving the pennies for a 3.2, accident damaged or ex-plod... by the time I've pulled the engine to bits and reassembled, I might as well fit the bigger complete unit... rebuilt while it's on the deck.

 Plus I'll get a new coffee table out of the 2.6 block...

[Kevin Wood]

Engines have survived this before... Worth a try turning that cylinder to TDC and seeing if you can see any debris. A small diameter hose connected to a vacuum cleaner will get any remnants out, then compression check it to see if there's a serious problem. If not, I'd be tempted to chuck a new set of plugs in and see how it goes.

Kevin

[vauxfan2k]

this happened to my elite before I bought it, hey couldnt get the bits out as they had melted onto the face of the piston, so seeing as it was a vauxhall garage that had carried out the service, the piston was replaced f.o.c. car has been perfect ever since.

[GastronomicKleptomaniac]

Pssht, by the time I've done everything else it needs, including cam cover gaskets (using proper VX sealant, unlike the garage did)... and I've always wanted to 3.2 it anyway...

[GastronomicKleptomaniac]

Right, I've borrowed a boroscope and had a look in the cylinder, it looks like all four valves have impacted the piston... there's no cutouts in the top of the pistons to allow for the valves, is there?

[Marks DTM Calib]

Right, I've borrowed a boroscope and had a look in the cylinder, it looks like all four valves have impacted the piston... there's no cutouts in the top of the pistons to allow for the valves, is there?

 

Yes.....certainly on the 2.5 and 3.0's

[GastronomicKleptomaniac]

Right, I've borrowed a boroscope and had a look in the cylinder, it looks like all four valves have impacted the piston... there's no cutouts in the top of the pistons to allow for the valves, is there?

 

Yes.....certainly on the 2.5 and 3.0's

D'oh. That'll be why they're symmetrical and still straight, then.

[Marks DTM Calib]

Lol....when you get impact damage its VERY obvious!

[GastronomicKleptomaniac]

In that case, I'm at a loss to explain why the spark plug has been impacted - I thought it was clear part failure, but on closer inspection it's sheared the top end clean off, with a clean break on all four electrodes... any ideas?

[MutantCav]

Sometimes they break when removing them...might have been ok but fragile until then...

[Marks DTM Calib]

In that case, I'm at a loss to explain why the spark plug has been impacted - I thought it was clear part failure, but on closer inspection it's sheared the top end clean off, with a clean break on all four electrodes... any ideas?

Cant see how the piston can hit the electrodes.

When fitted, only the electrodes are exoposed and even that sits within the combustion bowl!

Any sign of damage to the inlet valve guides on the cylinder (look down the inlet port associated with that cylinder using a good torch)

How old are the plugs and were they tight?

[GastronomicKleptomaniac]

No sign of damage to the valves, had a look with the boroscope. I'm at the point now where I'm so far into it, I'm going to a fit the 3.2 regardless... I need a new coffee table anyway.