im rebuilding my b18b1 with new rods and piston oem spec and and a semi built head, my question is will i need to balance my crank even if i’m putting pistons that are oem spec or will i have to get them balanced to the same weight as my stock ones and balance my crank(only looking for 200-300hp range boosted)

 

It never hurts to have a crank checked for proper balance. In addition, I would check the weight of each rod, each piston, and each pin... and then assemble them in an order that creates complete assemblies that are most closely weighted. Balancing this way provides a path where you can change out individual parts without having to re-balance everything.