Ensure the head is clean before reassembly, even if it was sent for valve servicing. If so, valves and components will be in place. Check the valve spring height with a caliper. Install new seals on valve guides, distinguishing intake and exhaust seals. Tap each intake valve seat into place. Use a socket and hammer to tap valve seals into place. Apply grease or oil to the valve stem before installing the first valve. Place the spring seat or shim(s) over the valve guide and set the spring and retainer. Compress the springs with a compressor and install the keepers. Release the compressor slowly and ensure keepers seat properly. Apply grease to each keeper if needed. Repeat for remaining valves, returning components to original locations. Check the valve spring height again with a caliper.