Ya need a 1/4-20 helicoil kit. It'll have the drill bit, tap, coils, and inserter. In tight areas I've used vise grips on the drill bit to drill, you might want to step drill it up to that size. that will make it easier to do. drills will follow the center of the hole so you don't really have much of an alignment problem. When tapping use a small wrench or adjustable, use something square beside the tap to get alignment and checkit from side and front every 1/4 turn. you don't need to take the cam cover off, just the tappet block out.If you don't have a blind hole, grease up a paper towel and stuff it in the case under the hole to catch chips and use grease on the tap, 2 turns of the tap only, remove, clean the tap and regrease, cut 2 more turns, clean and regrease til you hit bottom or finnish on an open hole. Tape off the tappet block hole before you start tappingCarb clean it and blow out with air, insert the insert one full thread below the surface and knock the tang off with a punch and make sure you find the tang so you can throw it away. Tang is magnetic so you can put a magnet under the hole to help capture it. New gasket, pushrod seals, and keep retorquing after heat soaks. A Helicoil kit is a good investment, they're around $30 and have 10 or 12 coils in it.