I've installed a Spec 2 clutch to my car but during launching the car shakes and rattles very badly I have to rev the engine and lift the clutch very qucikly in order to avoid the shaking. Also when downshifting if I didn't rev the engine it rattles and makes strange noises.

The flywheel is not resurfaced, could it be the reason if its the reason is there a possibility of damaging any other mechanical part in the engine or drivetrain because of this rattles and shaking?

 

Resurfacing the flywheel helps to break in the clutch, and get the best performance out of it. That very well could be your problem. After that much work, I would never take my chances not resurfacing it

 

is it possible that there is something not balanced correctly?(a loose screw or something) i'd try not to drive on it too hard and wait for the experts on this one.

 

I just had the exact same problem after installing my clutch. Turned out I torqued the pressure plate unevenly casuing it to be unbalanced on the input shaft and unable to disengage the clutch fully during shifts. I just retorqued it in a star pattern to specs and all the vibration went away.

Max