The valve mechanism elements must be clean from carbon and dirt I the same way that the bare cylinder head must be clean to the extent that there is no trace of any abrasive agents used in the grinding or reaming of the valves. Place a valve into the proper port and on the Oldsmobile engines compress a new seal over the valve stem and down into the head. Prepare the valve spring assembly for that cylinder; then clamp the assembly over the valve stem by means of a valve spring compressor. For engines of Chevrolet, replace the oil seal, placing it in the lower groove of the valve stem, and make certain that it does not twist. Last turn the valve locks and turn off the compressor until the lock sits in the upper slot of the valve stem.