GM 12617048 Exhaust Valve

Check the heads of the valves for pits, burns particularly on the exhaust valves and check the valve seating. If pitting is very minor it can be corrected by valve grinding the seats and the valves using coarse and fine valve grinding paste. To grind the valves, rub some carborundum paste of relatively large grain on the seat face and use suction grinder for the valve head using semi-rotary movement; once in a while, lift the valve head to let the paste spread evenly. When you get a smooth flat surface on the valve seat as well as on the valve face, remove the paste and wash it, then apply fine carborundum paste on the both surfaces and operate the valve lifting it up and turning as desired. For this purpose, it is possible to use a light spring under the valve head. When on both sides there is a continuous line of light grey matte finish the grinding process is said to be over. If there is deep pitting and burning-the valve must be refaced by the dealer and the seat recut; in case after refacing the head edge of the valve is worn down to the specified norms the valve must be changed. Free all carbon from both the valve head and stem and be certain that no grinding compound is in the ports or the valve guides. Scrub the valves and seats with a rag soaked in solvent, and then with a fresh clean rag; retire the valves and, if possible, use an air line to blow out any shooting from the valves, guides and ports.