MG Car Repair: Cross threaded spark plug, ft lbs torque, yamaha motorcycle dealer

Question
As my 79 midget had been stood for a year before I bought it, I decided to change the oil plugs and points. The third plug seemed stiff, so I undid it cautiously, but when I went to put the new one in, it was cross threaded and the old one didn't want to go back in either ! - short of taking the head off and getting it either drilled and shim installed, or trying to recut the existing thread with the head off - is there anything else I can do ? I don't want to take it apart if there is anything else I can do ...

Answer
Hi Ern,
It depends on how badly the threads are damaged. Here is a trick some mechanics use. Put that piston at TDC of the COMPRESSION stroke. Cut a shop rag (not the paper kind) in half and stuff the half into the plug hole all the way in. Then take a grease gun and pump several hand pumps of bearing grease in after the rag. Now carefully and straight, run a 14mm plug thread chaser in by turning it a quarter turn in and an eighth turn out until you get it all the way in. (To keep it in line it sometimes helps to start a plug in the hole next to it so you can reference the correct alignment with the tool. If you can get the thread chaser all the way in, remove the tool and with a short sharp bend on a coat hanger reach into the grease and hook the rag and pull it out. Even an experienced mechanic can't save all like this but most are saved. The grease catches the filings and the rag pulls most of the grease out. Then get and coat all the plug threads with "Never Seeze" available at most auto parts stores. Don't use grease as that will cause the plugs to freeze in the hole. Only apply about 25 ft. lbs. torque when tightening plugs. If this don't do the trick your next step is to either remove the head or check with a Yamaha motorcycle dealer as they use to sell a kit for repairing 14mm x 3/4 reach plug holes with an insert. Many auto machine shops have these kits too.
Howard