Galled Spark Plug
 

I pulled the spark plugs on my 84 ROW Targa last night (owned it a couple of months) and the No. 2 plug came out with the threads all chewed up. It was cold when I pulled the plug, the rest came out fine. Can I use a thread chasing tap with the engine in the car?, should I remove the valve cover first? will it give me better access? Please help. :eek:

Would the thread chaser not possibly be dropping shavings into the cylinder if it meets resistance?

If I am not mistaken, is this not done by overtorquing the plug?

And this is one reason why many of us advocate the use of a little copper or graphite, Nevr-Seez on plug threads.
(Yeah I know about Porsche and the Big Bird saying it will hurt the grounding of the plug. That is, of course, nonsense.)

If you use a thread chaser load it up with a heavy grease to hold any metal that it breaks loose.

Be sure to use a "chase" not a "tap", load it with heavy grease as previously suggested (I'd use wheel bearing grease, it's thick and sticky), be sure to get the chase started straight and correctly (you don't want to make your situation worse). If you can't get the chase to start correctly through the hole in the shrouding, you'll have to strip that side of the engine until you can start the chase directly into the plug opening. Use anti-seize on the plugs in the future and keep in mind to be especially careful on that hole. Unfortunately, if the head is too badly damaged this may not work, you'll have to remove it and have it repaired.

Good luck,
Jerry M
'78 SC

Thanks for the advise, especially the part about the heavy grease, I wouldn't have thought of that!!!

Another shade tree mechanic trick is to rotate the engine until the cylinder to be worked on has the exhaust valve open and hook a shop vac up to the tail pipe in the blow mode. This will give a constant stream of air coming thru the hole you are tapping. Watch out for metal shavings in the eyes!

Damn plugs always gall up at the most inoportune time. I had one do that 5 minutes before time to line up on the grid at a race at the old Riverside track. I made the race. Lots of panic fixing the threads. This was in a kart, BTW. I wish I drove Riverside in a car, but never did.