A hand tool that greatly expedites the installation of the valve locks that secure a valve spring retainer to the free end of a valve stem. The valve locks include an inwardly extending ridge that engages a circumferential groove that extends around an end portion of the valve stem. The valve lock is retained in this position by a tapered central bore of the valve spring retainer that produces an inward clamping force on the valve lock. The tool includes a plunger having a diameter equal to the diameter of the valve stem. The user positions the valve locks on the protruding cylindrical surface of the plunger, where they are held by magnetic attraction. The user pushes the end of the tool against the valve spring retainer, thereby compressing the valve spring so that the valve stem pushes the plunger into a close-fitting loader end cap until the valve locks are transferred to the valve stem and into engagement with the circumferential groove.