Wow, no more spark plug threads (in the head), '88 5kcstq

[Ken Keith]

Hi List:

Damn.  I noticed a ticking noise that was intermittent on my '88 
5kcstq.  I was thinking I had an EM crack, which I may still have.  
Anyhow, I didn't think the ticking should be intermittent on a warm 
engine.

I popped the hood and saw my number five spark plug wire moving 
up and down.  I thought the wire itself was loose, but it turned out 
the plug was loose.

I pulled everything apart and removed all the plugs.  I found out my 
number five plug hole no longer had any threads in it for the spark 
plug!  Holy crap!  Surreality sets in.

I read some posts in the archives, like the "blew a spark plug" 
thread, so I think I should be able to helicoil or timesert it.  I don't 
know if I want to undertake it myself, or have it done professionally.

How difficult is it to get perfect alignment for these types of things?

It seems I've been going about one and a half to two weeks 
between downtimes on this car.  I would have never expected to 
have the plug threads go away on me.  It was quite a while ago that 
I had changed the plugs.  I was going to put new ones in, tho' they 
weren't that bad.  I'm running W7DTC's.

Also, I looked through my (earlier single volume) Bentley for the 
car, and couldn't find anywhere the plug torque spec, or any 
reference at all to spark plugs!  I was amazed.  This was before I 
actually went to put the plugs back in.

Would the very fine aluminum shavings that were built up around 
the stripped plug hole, be a threat to the motor or turbo if they 
made their way into the CC?

I guess I'm still optimistic.  At least if the plug have hanging out, it 
would explain why the car didn't seem as fast.

Should I assume that it was a freak occurence, or is there 
something that would have caused this to happen?  Overtorquing, 
crossthreading, pinging?  I doubt I overtorqued or crossthreaded the 
plugs.  Could undertorquing cause it to happen?  It seems if the 
plug worked its way loose, then it would vibrate and machine its 
way through the threads, also eroded by combustion flame?

Should I just repair the one hole that is damaged, or is there any 
virtue in doing all of them, since some thread repairs are supposed 
to be stronger than original threads?

Anyone got a cheap used MC head they don't need?  Maybe I'll 
pull it and swap in a better head or something.  LMK if you have 
one, please.

Thanks,

Ken
'88 5kcstq, down again!
'94 SL2, commuting again
'85 4ksq, still waiting
'87 5kt, now missing radiator and waiting