helicoil in heads

hi,

I had a intake manifold leak and took the intake off. Also, each head has one set of threads that have stripped out that hold the valve covers on. I was planning on taking the heads off as well to put the heli coils in, but now i see that the holes do have a bottom to them. Is it safe to drill and tap these holes with a couple magnets close by to pick up the metal coming out? or is the chance of getting metal filings into the engine too high?

I ordered new head gaskets and will have them if i need them, i am just trying to save some work.

Laziness never pays off does it?

Anyway, here are some pictures

Thanks,

Steve