One of the most commonly serviced parts of an engine is the cylinder head. It is often removed either for modifications (such as porting), replaced with a different design, or to facilitate a repair (as when a head gasket fails). Regardless of the work being performed, the cylinder head requires special service to guarantee not only that the deck surface is true, but also proper valve action and sealing.

The cylinder head can be brought to the machine shop either assembled or disassembled. If you decide to disassemble the cylinder head yourself; keep the valves, locks, springs, and retainers together for each port. Do not throw everything into a box, but instead number each group of components with its location. For example, #1 intake, #7 exhaust. This will allow the machinist to diagnose any wear problems and perform accurate corrective procedures. Remember, when it comes to engines, every part tells a story.

Once the machine shop receives the cylinder head, they will do a visual inspection to look for damage, such as cracks and valve recession. When recession occurs the valve will actually pull through the cylinder head at the seat. This is shown on the surface the valve closes against. Next, the head will be taken apart and cleaned. Cast iron heads can be Magnafluxed using the same procedures that were established in Part 1 of this series. Aluminum cylinder heads need to be pressure checked using an application-specific machine to confirm no cracks exist.

FINISHING UP AND STORING COMPLETED HEADS
When all of the machine work is done, the cylinder head will be cleaned and assembled. The valves will be lubricated with a white lithium or low-fiber grease. The springs will be installed in their proper predetermined location, and possibly shimmed for pressure and correct installed height. Whenever a cylinder head is taken apart, it is advisable to use new valve stem locks and guide seals. The cylinder head may then be coated with an anti-rust spray (like a penetrating oil) and packaged in a clean, sealed plastic bag, awaiting installation. Heads can be stored, after being sprayed with oil, and sealed in a plastic bag indefinitely.

 

 

 

REPLACING PRESS-IN STUDS WITH SCREW IN STUDS
Most production cast iron cylinder heads have rocker studs that are interference or press-fit into a boss that is cast into the cylinder head. A stud puller is required to remove them. The new stud is then pressed into place using either a hydraulic or arbor press and lubricating oil. Press-in studs can be converted to screw in studs by first removing the old stud and then drilling and tapping the created hole. Many try this at home with mixed success, but any machine shop should be able to accomplish this procedure without fanfare or great expense. If you plan on upgrading your springs, increasing your rocker ratio, or spinning the engine past 5,500 rpm with any regularity, you should upgrade your rocker studs from press-ins to screw in types. Otherwise, they'll probably start pulling themselves out for you.

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