Regardless of whether the head was sent to an automotive repair shop for valve servicing, ensure it is clean before beginning reassembly. If the head was sent out for valve servicing, the valves and related components will already be in place. Starting at one end of the head, lubricate and install the first valve, applying moly-base grease or clean engine oil to the valve stem. Slide a new valve stem seal over the valve and seat it on the guide using a deep socket and hammer, gently tapping the seal until it is completely seated on the guide, taking care not to deform or cock the seal during installation. Note that on some engines, the intake and exhaust valve seals may differ. Install the valve spring seats or shims if applicable, then set the valve spring damper and retainer in place. Compress the springs with a valve spring compressor, position the keepers in the valve stem grooves, and slowly release the compressor, ensuring the keepers seat properly. A small dab of grease can be applied to each keeper to hold it in place if necessary. Repeat this procedure for each valve, ensuring that components are returned to their original locations without mixing them up. Check the installed valve spring height with a ruler graduated in 1/64-inch increments or a dial caliper; if the head was sent out for service work, the installed height should be correct, but do not automatically assume it is. The measurement is taken from the underside of the spring damper to the underside of the spring retainer. If the height exceeds specifications, shims can be added under the springs to correct it, but do not shim the springs to the point where the installed height is less than specified.