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[Marks DTM Calib]

So the foreign object has caught the seat resulting in some minor valve erosion, how deep is that erosion?

[aaronjb]

Er no, fit plugs, turn head over and fill combustion chambers with a suitable fluid (not water). 

*facepalm* D'oh, yeah.. I had that thought riiight after I hit Post and walked away Failure to engage brain before posting on my part (I was thinking cylinder leak down test)

[JamesV6CDX]

So the foreign object has caught the seat resulting in some minor valve erosion, how deep is that erosion?

It's not enormous, but noticible. I can't find any other cause for the low compression on that cylinder

I wanted to find something more conclusive, really

[JamesV6CDX]

Ps valve guides nice and tight...

[Marks DTM Calib]

Ps valve guides nice and tight...

Nice and tight or to tight?

[JamesV6CDX]

As in spot on, I've rebuilt a few of these heads and feels fine by my (albeit DIY) experience

Shall we just fit the known good head now and see what happens? 

[JamesV6CDX]

Ok new head all cleaned, just off to pressure wash it and we will see what happens tomorrow

[EMD]

So the foreign object has caught the seat resulting in some minor valve erosion, how deep is that erosion?

Seen exactly the same when i took the head off a Vectra B , never did find what caused it 

[Steve B]

James Do you think the foreign Objects Had to be harder than the surfaces that have been damaged

[05omegav6]

James Do you think the foreign Objects Had to be harder than the surfaces that have been damaged

The electrodes on a spark plug could easily do that as they and the pistons are steel, whereas the head is soft as toffee aluminum

[Steve B]

James Do you think the foreign Objects Had to be harder than the surfaces that have been damaged

The electrodes on a spark plug could easily do that as they and the pistons are steel, whereas the head is soft as toffee aluminum

And what possible situation could there be where 3 electrodes have all came off 

[05omegav6]

James Do you think the foreign Objects Had to be harder than the surfaces that have been damaged

The electrodes on a spark plug could easily do that as they and the pistons are steel, whereas the head is soft as toffee aluminum

And what possible situation could there be where 3 electrodes have all came off 

Crap plugs 

That said, mine were GM twins... but all were loose after only 500 miles. So wonder if the electrical issue causes it to run lean, knackering the plugs due to a weak spark, leading to them going brittle and falling apart...

Anything in your history regarding investigative head/cam work? For the cam caps to be fitted wrongly to wear as they have (as per Marks suggestion), could the cams have been removed to check the lifters?

If the only cam history is when you put the car in for a cambelt/service, how long did they have the car for? Someone might have been trying to hide summat

[JamesV6CDX]

James Do you think the foreign Objects Had to be harder than the surfaces that have been damaged

The electrodes on a spark plug could easily do that as they and the pistons are steel, whereas the head is soft as toffee aluminum

And what possible situation could there be where 3 electrodes have all came off 

Crap plugs 

That said, mine were GM twins... but all were loose after only 500 miles. So wonder if the electrical issue causes it to run lean, knackering the plugs due to a weak spark, leading to them going brittle and falling apart...

Anything in your history regarding investigative head/cam work? For the cam caps to be fitted wrongly to wear as they have (as per Marks suggestion), could the cams have been removed to check the lifters?

If the only cam history is when you put the car in for a cambelt/service, how long did they have the car for? Someone might have been trying to hide summat

The cam shells were all in the correct orientation and positions when we stripped it..

Even if it were three plugs that failed...

The question remains unanswered - why was this car having no problems prior to the Cambelt/service/camcovers/stat work - and making nasty metallic noises + misfiring the minute the key was turned after the work?

I'm only asking the question for one reason - to get to the bottom of the fault.

It's just too big a co incidence IMHO that it was fine before the work and so rough straight after

[chrisgixer]

I've seen three engines with similar damage listed on here.

Mick Dundees
Taxi Al's
This one belonging to Bigtime.

Why have all three involved the 246 bank? It can't all be to do with access and the cable tray, surely?

[05omegav6]

Any word on previous work?