Just checked my plugs and all were as tight as can be. Even the damn spark plug cover was tight, so much so that I spent the most time loosening the bolts on that...

 

I've been giving Greg's experience some more thought. I completely agree that the plug must have been blown out of its hole so forcefully that it bent, smashed the coil, and dropped bits of shattered porcelain back into the cylinder.

But I think there might have been more to it -- based on long-past experience with a 1970 VW. This car repeatedly blew its #4 plug, though there was no destruction because there was nothing to keep the plug near the hole. It would just blew out with a big noise. I would stop, find it dangling from its wire, put it back in, and drive away. Each time it happened it became more and more difficult to put it back until I realized -- voila -- it had been cross-threaded and the threads in the head were destroyed. I finally fixed it by tapping the threads (VERY carefully, with lots of heavy grease to hold the shavings) and inserting a helicoil.

It finally dawned on me that the plug started popping out in the first place because of the cross-threading. It couldn't be screwed in very far, the aluminum head expanded more than the steel plug base when the engine heated up, and boom!

All this makes me wonder if Greg's #1 cylinder didn't have a cross-threaded plug that caused this mess. That would also explain the missing threads in the head.

 

[QUOTE]Originally posted by DouglaS2000
[B]Just checked my plugs and all were as tight as can be.

 

Whew. Lot of theory here. So here's some more:
1. The spark plug will always retain threads (steel) while the (aluminum) head will strip.
2. The way the threads stripped was that the plug was either overtightened by a person (and yes, I wouldn't recommend that everyone on this board do it without a torque wrench and yes, you'll know jiffy-quick if you strip it.) OR LIKELY,
3. The loose plug bounced up and down on every power stroke, banging against the threads in the head and slowly jackhammered them out. I don't see why this wouldn't be likely.

Threads are always cut with the same thread angle but slight tolerance between the lands and grooves. "Lands" are the top of the thread, "grooves" are the inside v point. Without tolerance between the outside land diameter and the inside groove diameter, you wouldn't be able to turn the fastner.

BTW, mine were fine and I'm starting a poll on this.

 

Just to add my experience, I had mine checked today at the dealer. The front 2 were finger tight, while the back 2 were perfect. ofcourse the service guys were all clueless as to the reasoning.

 

Service guys are pretty much always clueless. They need no reason.

 

Just finished checking mine - all were torqued fine.

Here's the process I used:

Cool engine.

3/8 drive used. Removed the four plug cover plate hexagon bolts using 5mm hex bit (A set of metric hex bits was $23 at Lowes or $28 at Sears).

Remove the plate following the instructions on page 174 of the owner's manual.

Loosened the four 10mm bolts holding the coil/plug assembly. Be careful not to drop any bolts and set them aside where they won't be bumped into the engine compartment.

Taking one coil/plug assembly at a time follow the manual and detach the wire and remove the coil and check the torque setting.
I used an 8" extension with a 5/8 spark plug socket. Replace everything and move on to the next one.

I had no problems with #1 to 3; however, #4 would not co-operate. The torque checked out ok but every time I tried to withdraw the socket, it would not come out.

I tried using extended fingers, a magnet on a telescope handle, etc. Finally I just loosened up the plug and removed both the socket and plug. Put on some antisieze. Reinstalled the plug and the same thing happened again. So I removed the socket/plug combo again and it's setting on the work bench.

Back in the old days when guy's used to work on Hemi's they would weld a sock to an extension for this very reason, so I may be forced to do that. The socket is a Craftsman with the rubber inside but it does not have a specific hole drilled into it to accept the locking ball. Maybe a better style socket is needed for this job. Whatever, I thought I would share my experience.

 

[QUOTE]Originally posted by dlq04
[B]Just finished checking mine - all were torqued fine.

 

[QUOTE]Originally posted by xviper
[B]
Hold the socket onto the extension with a piece of duct tape.

 

quote:
__________________________________________________ _____________________
dlq04 Back in the old days when guy's used to work on Hemi's they would weld a sock to an extension for this very reason, so I may be forced to do that. The socket is a Craftsman with the rubber inside but it does not have a specific hole drilled into it to accept the locking ball. Maybe a better style socket is needed for this job. Whatever, I thought I would share my experience.
__________________________________________________ _____________________

I usually just tighten the plug up and then very slightly turn the socket (not the plug) backwards to break it loose from the plug.

Bob