The cylinder head of a car's engine is prone to a build-up of sediment and rust that will impede not only the movement of the valves in the cylinders but the passage of coolant and oil in the engine block. The best way to maintain a clean cylinder head is to make the process a part of your regular annual maintenance. You can clean a cylinder head easily, but if you don't do it on a regular basis you'll have to take it to a machine shop.
Using your socket set, remove the air cleaner and valve assembly from the top of the engine block. Unbolt and remove the cylinder head.
Spray the B-12 Chemtool Carburetor Cleaner in every orifice of the cylinder head, paying particular attention to the coolant and oil passages cast into the head. You will not be able to see into these passages to verify how clean they are, so make sure they receive the most B-12 to try and ensure a good cleaning.
Wipe the cylinder heads clean with a rag. If any sediment is still attached to the head after spraying it, gently scrape it off with a flathead screwdriver. Spray compressed air into the oil and coolant passages to clean any loosened deposits from them.
Spray everything again with B-12 and repeat the cleaning process. You want the cylinder head as clean as possible.
Examine your cylinder head closely. If you still see significant deposits, take it to a machine shop to be cleaned with acid baths and beading machines. There is a limit to what you can clean by hand.
Set your cylinder head up on small blocks of wood so it can drain easily as you spray the B-12. This will also help you detect any clogged passages because they will not drain as easily as the others.
Never tap a cylinder head to dislodge sediment. Because you cannot see into the oil and coolant passages, you may dislodge something that will block the passage, causing the car to overheat.