I’ am rebuilding a 13B Turbo motor
I got a few water seal that look like new
But that are all about 1-2cm too big
Dose any one knows how to skink the water seal back to the normal size? or
And has any one try to cut a bit out of the o’ring to make it fit
What are the chances of that working?

 

Would you reuse a rubber?
Don't even try it unless you want engine failure real soon.

 

I'm surprised you even think about the possibility!
Replace all of the o-rings, seals ++. You don't want to rebuild the engine a second time!