[kirkwood158]

get heli-coil kit for the size you need and try drilling with that as it will replace the same size threads you need for plugs but will drill a larger hole to get plug out and the coil will put threads back to same size . (ask at auto parts store take plugs with you) ONLY problem is metal shavings and you must get as much out of the cylinder as possible. suggest bringing cylinder that is effected to TDC first then drilling and vaccumimg out even if you have to buy some attachments and vac. at hardware store and I know lowes has a good attachment set for small opening that will fit a good size vac. check it out ....been there dun that