Is it possible to split bike calipers into two halfs? I was thinking about using calipers from a bike and split them and make a an aluminum distance to make them wider to accept discs from a car.

Most modern bike calipers slip in half to enable them to be resealed/rebuilt etc. They need this often as the seal design allows for dirt ingress if they are not rigorously maintained.
I wouldn't bother using them if I were you. Use some aftermarket billet calipers such as hi-spec or willwood if you want top brakes on your car as a set of seals alone can cost nearly £ 100

Whooho.. thats kind of expensive.. Well I got to think about it cause my dad is a bike mechanic so he might be able to get me a used couple quite cheap.

Bike callipers was something I was considering as a lightweight alternative- Rorty has talked about using them- he has custom discs laser cut for him.

If Tim's right about the cost of maintenance maybe I won't look any further though!

James