So I'm happily driving down the road in my 96 VDP with only 66k miles at about 75mph or so just loping along and all of a sudden it starts missing... then it get's worse... and worse.... when I get it stopped I find out that 3 champion spark plugs are blown apart. And one of the spark plug wells seal is torn off inside. There's pieces of Porcelain in the cylinders and a couple pieces of the metal post. I get them out with a magnet blow out the porcelain by running it with the spark plug wells open (white stuff flying out) The coils are burned and the boots torn. #2 #3 and #4 blew apart. I've got the valve cover off now and am waiting for new seals boots and with new plugs I think she'll be ok. BUT... has any one ever had spark plugs fly apart like that? And no the cylinders and valves are fine and the timing is great. luckily no serious damage.
I'll never use champion plugs again. They were old yes but geeze they only had about 20K miles on them.
Stupid plugs gave my car a serious boo boo.
And my pristine valve cover is ruined. as it was coming apart sparks tore into the magnesium. even had some flames as the unburnt gas ignited under the cover.
all's well but it could have been worse.

#2 blew the gasket out

#2 #3 #4 all looked like this or worse! Champion plugs at their finest!!!

 

when you say old how old do you mean?
materials degrade with age often more so than they do with use.

the only time i have seen anything similar to this is when the sparkplugs were not firmly secured. therefore not being able to properly transfer the current to the engine and then exploding due to a build up of current. this is something that would happen generally with them being loose for sometime and slowly wearing down the sparkplug till it becomes much more brittle.

i find it hard to blame the brand of plugs as i have certainly never heard of this before and lots of people seem to say to ensure to use the champion plugs for best running of the car. if this were an issue of the brand of plugs then this would not be the sentiment attached to them.

 

I have never experienced or heard of anything like this. One rogue spark plug once in a blue moon, maybe, but three in adjoining cylinders, giving up the ghost more or less simultaneously.........?
Is there a back story here? Had the engine recently been pressure washed for instance?

 

I had an unpleasant experience with Champion plug as well before but the real culprit could be a bad coil. See my old post a couple of years ago below.
https://www.jaguarforums.com/forum/x...-meter-201538/

 

Likewise with a Bosch, one only, on one of the V12's. They run 12.5:1 comp, so any weakness, oops.

I would be checking, and even for the hell of it, fitting a second engine to chassis earth strap.
Lack of earth with high current like they run, would cause all sorts of grief.

 

They were about 6 years old with about 20K miles on them. 1/4 a turn past stop just enough to be stiff on a 3/8th drive.

 

The coils we replaced with the good Jap coils about 20K miles ago. That was at the same time as the plugs. I still have the factory originals in a box but they were 20 years old so I replaced them for good measure when I bought the car. It had been sitting in a storage unit for about 15 years so I had lots of work to do replacing everything rubber on the car for instance.

 

Wow that looks exactly like mine... I'm going to replace the coils again before it happens AGAIN!!! OMG!
That's why one blew after the other I'll bet. I'm going to check my grounds!

 

Happened to me one time (but only to one spark plug), with Champions. I switched to NGK.