i pulled the motor on my civic because i noticed that i was missing the woodruff key and my crank snout was missing a decent sized chunk out of it, ill provide pictures when i get home. i know its kinda hard to say without pictures but would i able to weld it and make the key fit right or do i absolutely have to replace the crankshaft?

 

If the left side of the keyway slot is undamaged, then you can effectively weld up and re-cut the keyway slot using the left edge as your guide. The important issue is that if the entire slot is damaged, how can you be sure that the new keyway is in fact in the exact location to represent TDC ? If you don't feel that the repair can be done without being certain that the key slot is properly indexed, then you should replace the crankshaft.