| Engine Valves |
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The valve train includes the camshaft, valves, valve springs, rocker arms, retainers, and
keepers. If the camshaft is mounted in the cylinder block it will have push rods and lifters
as well.
After cleaning and buffing on the wire wheel the valve should be inspected for:
No margin: The margin of the valve will get pounded away in time and if the margin is to
thin the valve will heat up and burn prematurely.
Pitting, Burning, Cracks: This usually happens to the exhaust valve because they tend
to get hotter. Exhaust valves are usually made out of high quality stainless steel but don't
benefit from the cool air and fuel the intake valve receives on the intake stroke.
Cupped Heads: Once the head is cupped or mushroomed the valve must be replaced.
Stretching: Stretching is the narrowing of the neck above the head of the valve. This
effects the length of the valve affecting its geometry.
Worn Keeper Grooves or Valve Stem Tip: Look for worn keeper grooves, rotators,
and retainers and replace if any of these are worn. If a keeper or retainer pops out of
place the valve will drop in the cylinder causing engine damage. A worn valve stem tip will
cause retainer and rocker arm damage.
Valve Stem: The valve stem should be measured with an outside micrometer in several
places to check for uneven or excessive wear.
Valve Springs should be checked for their installed height which is from the base or
pocket in the head to the bottom of the retainer. If this height is excessive a shim must be
added to bring the spring back to its proper tension. When placed on a flat surface the
springs should remain square and any short ones (*1/16 inch) should be replaced.
Tension may also be checked with a valve spring tester.
keepers. If the camshaft is mounted in the cylinder block it will have push rods and lifters
as well.
After cleaning and buffing on the wire wheel the valve should be inspected for:
No margin: The margin of the valve will get pounded away in time and if the margin is to
thin the valve will heat up and burn prematurely.
Pitting, Burning, Cracks: This usually happens to the exhaust valve because they tend
to get hotter. Exhaust valves are usually made out of high quality stainless steel but don't
benefit from the cool air and fuel the intake valve receives on the intake stroke.
Cupped Heads: Once the head is cupped or mushroomed the valve must be replaced.
Stretching: Stretching is the narrowing of the neck above the head of the valve. This
effects the length of the valve affecting its geometry.
Worn Keeper Grooves or Valve Stem Tip: Look for worn keeper grooves, rotators,
and retainers and replace if any of these are worn. If a keeper or retainer pops out of
place the valve will drop in the cylinder causing engine damage. A worn valve stem tip will
cause retainer and rocker arm damage.
Valve Stem: The valve stem should be measured with an outside micrometer in several
places to check for uneven or excessive wear.
Valve Springs should be checked for their installed height which is from the base or
pocket in the head to the bottom of the retainer. If this height is excessive a shim must be
added to bring the spring back to its proper tension. When placed on a flat surface the
springs should remain square and any short ones (*1/16 inch) should be replaced.
Tension may also be checked with a valve spring tester.