This can only happen to me

[Brian 162]

The weirdest things that go wrong on my SC happen to me.
A bit of history. I left my car so my mechanic could adjust the valves and install a strut bar. A week after I noticed a big exhaust leak. A small plug in the head fell off. I think it was used for air injection. I made the repair and every thing was o/k.
I've maybe put 50 miles since the repair.
Took the car out today and after an hour of driving I heard a loud exhaust leak. It couldn't be the same thing. This time the car wouldn't idle.
I had to jam a piece of wood on the accelerator so the car would run so I could check things out.
Somehow the spark plug on cylinder #6 came out. I pulled the ignition lead with the plug attached.
Re-installed and checked the rest of the plugs and all is good.



Has anyone seen this happen before?

[schumicat]

i think someone reported the same thing a month or so ago. likely wasn't torqued properly in the first place.

[Bob Kontak]

Damn, that engine is clean.

[Brian 162]

Originally Posted by Bob Kontak

Damn, that engine is clean.

I maybe drive 2000 miles a year, most of that being track days.

[Porchdog]

+1 on that clean engine.

[Brian 162]

Thanks, I try to keep the engine clean. Thankfully the oil leaks are on the bottom of the engine. I took this picture today.

[Quicksilver]

I had one come out about 8-10 years ago. Sounded like a machine gun. Never did figure out why. The plug had been in for at least 5K miles so it seems really odd that it wouldn't have become more firmly seated after that quantity of time.

Put it back in and moved on/

[docrodg]

I recall reading about a performance engine (big block chevy) that had been converted to 4-valve hemispherical heads. Compression was astronomical and they were driving it hard when it shot out the plugs. Picture of the hood showed dents from their impact!

[HawgRyder]

Ejecting plugs used to be a problem with old flathead Harleys.
The threads in the head would pull out...and the fix was to install was to install a device that looked like an oversized heli-coil with a flange on it.
Lately...I have heard of threads pulling on several high compression engines...I think because they use the newer 10mm plugs which have less thread grab.
Obviously the longer the plug threads are (plug reach) the better the grip.
Some designs use a very short reach plug.
I think that the designers never imagined the ends that we as builders would go to "improve" their design.
I always use new plug washers on every install (they crush slightly) so that I get maximun grip.
Bob

[weseeeee]

I had to deal with the plug from the air pump falling out once but never a spark plug!

[zippy_gg]

Wondering if perhaps the plugs were installed with anti-size and under-torqued...

[RSTarga]

Normal procedure for adjusting the valves involves removing the plugs. I think your mechanic didn;t retorque properly.

[Brian 162]

Originally Posted by zippy_gg

Wondering if perhaps the plugs were installed with anti-size and under-torqued...

I checked the other plugs and they were fine. What I can't get my head around is how the plug loosened off while still attached to the plug wire.
Anyway all is good now.

[JJ 911SC]

Look like the mechanic got distracted after torquing #5 and did not get back to # 6