Q: Welding the harmonic balancer to crank shaft? 1991 Chevrolet S10

Hello - No, welding the harmonic balancer to the crankshaft is not a good idea for at least 2 reasons. Welding the balancer hub to the crankshaft will damage or reverse the benefits of heat-treatment to the crankshaft itself - possibly resulting in failure of the crankshaft. Second, many crankshaft harmonic balancers have a rubber ring in-between the hub, and the pulley portion of the damper. Welding the hub to the crank will almost certainly pass enough heat to the rubber portion of the balancer to damage it. Best to repair whatever situation is making you consider welding the harmonic balancer to the crankshaft. I recommend a crankshaft harmonic balancer replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, and replace your harmonic balancer.