Rocker arms must be removed to be inspected for wear and damage.
- Inspect the rocker shaft assembly for wear, especially at points that contact the valve stem and pushrod.
- The pushrod contact area of the rocker arm should be round and the wear even.
- Normal wear will result in a shiny surface. A ridge buildup around the pushrod contact area indicates the rocker was hammering too much valve lash.
- Pits, scores, and galling generally indicate lack of lubrication or excessive heat.
- Valve stem wear should be centered in the arm. If the wear is not centered, the rocker arm pivot may be worn or the stud may be bent.
- If these are good, then carefully inspect the valve guide and seat for wear.
- In addition to these checks, inspect the side of the rocker arm for indications of cracks.
- The fit between the cast rocker arm and the rocker shaft is checked by measuring the outside diameter of the shaft and comparing it to the inside diameter of the rocker arm. Excessive clearance requires replacement of the rocker arm or the rocker shaft, or both.
- Another wear point that should be checked is the pivot area of the rocker arm to rocker shaft.
- Stamped steel rocker arms are not resurfaceable and should be replaced if found to be worn.
A common area of wear is the rocker arm to rocker shaft pivot point.
- Other rocker arm wear points are shown below.
Rocker arm wear spots.
Lack of lubrication to rocker arms can cause a loud, "squeaky" sound in some older engines. This problem is not as common as it used to be, partly because of the better oils in use today.
The method the manufacturer uses to mount the rocker arm will require unique inspection procedures. Following are some of the additional inspections that should be made based on the type of mounting:
Shaft-mounted Rocker Arms
- Inspect the shaft for wear where the rocker arm pivots.
Shaft-mounted rocker arms.
- The shaft should be free of scoring or galling.
- Normal wear is indicated by slight polishing but no ridges. Wear in this location is usually due to lack of lubrication or excessive heat.
- Also check the shaft for warpage by simply rolling it on a flat surface (such as a sheet of glass).
- Shaft-to-bore clearance can be checked by using an outside micrometer to measure the diameter of the shaft where the rocker rides. use a bore gauge and zero it to the micrometer. insert the bore gauge into the rocker arm and note the dial reading. out-of-round can be checked at the same time as clearance. compare results to specifications. if wear is excessive, the rocker arm must be replaced.
Shaft-to-bore clearance and taper can be checked using an outside micrometer set to the size of the rocker arm shaft, then zeroing the bore gauge to the micrometer. Courtesy of Honda Motor Company.
- Typical oil clearance specification is a maximum of .005 in. (0.13 mm).
- Visually inspect the springs and spacers used to separate the rocker arms for warpage, breakage, scoring, and other types of unusual wear patterns.
- Replace any that are found to be defective or worn.
Stud-mounted and Pedestal-mounted Rocker Arms
Stud-mounted rocker arm. Reprinted with the permission of Ford Motor Company.
Pedestal-mounted rocker arm. Reprinted with the permission of Ford Motor Company.
- Stud-mounted rocker arms use a split ball for the pivot point of the rocker arm. Pedestal-mounted rocker arms are similar to the stud-mounted assembly, except the rocker pivots on a split shaft. With both of these styles, the pivot fulcrum must be inspected for wear.
Inspect the pivot fulcrum and contact surface for nicks, scoring, or scuffs. Reprinted with the permission of Ford Motor Company.
- Look for nicks, scoring, or scuffs. If the pivot or rocker arm is worn in these areas, replace both components.
- Scoring or scuffing indicates a lack of lubrication. Stud-mounted rocker arms can be lubricated through a hollow pushrod or by small holes drilled through the mounting stud. Pedestal-mounted rocker arms are usually lubricated by an oil passing through a hollow pushrod.
- If poor lubrication is suspected, the stud should be replaced.
- On positive stop rocker arm stud nuts, check the shoulder for damage or fractures.
Inspect the stud nuts for wear and damage. Reprinted with the permission of Ford Motor Company.
- Also check the rocker arm's contact surface with the pivot fulcrum. If the pivot or rocker arm is worn in this area, replace both components.