Building a model jet engine

Hi guys, this is my second attempt to built a successful model jet engine , and have some critical questions about that.

I attached some photos from my first attempt below if you want to take a look at. I believe that the engine was too small to self sustain, also i maid the turbine out of steel so it melted at the first start attempt :-( .

Now am trying to built a model jet engine based on an old compressor from a car the size is 66mm.

My questions are:

1) How mach critical is the gap between the compressor its cover?
2) Am trying to built the turbine out of stainless steel, I want to know if it is good enough to stand the high temperatures.
3) What ball bearings I should use?

Thank you very mach.