What should be verified about the valve tappets during installation?

During the installation of valve tappets, it is crucial that they are pushed in as far as they will go into the crankcase. This is important because proper seating ensures that the tappets have the correct engagement with the camshaft and that they can function smoothly within the engine's valve train system. If the tappets are not seated properly, it can lead to poor valve operation, excessive wear, and increased risk of engine damage. Ensuring they are fully seated helps maintain the necessary clearances and alignment for optimal performance.

The other options do not guide the installer towards the critical function of the tappets, and while securing them, lubricating, and aligning are important aspects of engine assembly, the primary concern during initial installation is ensuring they are fully inserted into the crankcase for proper functioning.