The machine shop showed me the heads that came off my engine that lost the head gasket on the cylinder that leaked the head had small peck marks all over it like i sucked something into that cylinder.

So I'm thinking what the hell could have gotten in there i went home setting at the work bench i say to myself maybe the spark plugs sure enough one half of a NGK iridium porcelain is missing probably because of the coolant in the cylinder.

Lucky for me the machine shop says the head is OK.

The porcelain is missing from the outside of the plug or the inside where the iridium point and strap are?

Glad the head can be repaired.

Matthew

I would have expected the porcelain part to have just shattered and broken up.

I wonder if the ground strap bounced around? or the electrode? Or something else entirely?

The inside porcelain split off lengthwise so it was a pretty big piece it spit it out the exhaust the electrode and ground strap are fine ill take a picture of the plug today if i have time i think ill be going back to the Autolite Spark Plugs.

I would contact NGK. If nothing else to let them know one of their plugs failed in this manner.

Was it the number 7 cylinder?

Number 8 cylinder.
I was thinking about calling them they would probably replace the plugs but i don't think i would want them after seeing that plug it broke off clean down both sides like maybe a flaw in the casting of the porcelain.

I had good luck with their customer service, but it was about product selection, not a flaw. Can't hurt to try.

Matthew

My only other thought is clearance... but if that was the case, I would be shocked if you indexed the other 7 perfectly!!

Here I thought you broke your toilet...

Seriously though, is it possible the broken plug caused the gasket to fail?

If possible post some pix of the head damage & the top of the piston.

SWAG: Water in the cylinder created steam during ignition. The ensuing shock wave from the steam expansion damaged the spark plug.