Do's and Don'ts For Fitting And Running In Camshafts.

As a critical engine component, camshafts should always be fitted in accordance with good engine building practices.

The camshaft is one component in a system and it must be checked that the camshaft is compatible with all other components including but not limited to: valve springs, lifters and push-rods.

Check for adequate clearance between all parts of the valve train and, any fixed part of the engine as well as all other components in the valve train.

New and re-profiled camshafts, in particular flat tappet style cams, should always be fitted with new or re-profiled lifters.

Mechanical tappets should be set as accurate as possible before starting the engine and bring up to temperature.

Hydraulic lifters should be bled down before assembly into the engine. These may well be noisy on start up but should quieten down within a few minutes. Pumped up hydraulic lifters will cause the valves to be held open, preventing the engine from starting.

The tight radius of the cam lobe nose has the smallest contact area of any part of the cam lobe and is most susceptible to damage during run in (break in). This area is highest loaded at low speed. To ensure the lobe and it's follower successfully run in, and to achieve maximum life span of the components, a few basic precautions must be taken.

Engines with high valve spring pressures will require lighter valve springs fitting for running in. With dual springs this can often be accomplished by temporarily removing the inner spring.

Cam lobes on non roller type camshafts should be lubricated with a quality moly (molybdenum disulphide) based lube that will adhere to the lobe until, and during, start up. The lifter face or rocker that runs against the cam lobe should also be liberally coated with lube.

The engine should be fitted with a new oil filter, and filled with new oil. Note that not all oils are suitable for the running in procedure. Kennelly Cams recommend using mineral oil for the running in of flat tappet and slipper type rocker engines, and if you do not know that the oil has a high zinc (ZDDP) content, Kennelly Cams recommend using an appropriate zinc additive.

Oil and fuel systems should be primed and ignition timing set statically before cranking the engine. Engine cranking time should be kept to a minimum, and slow speed operation must be avoided for the first 30 minutes of running. The engine should be immediately brought up to 2000 rpm upon start up and not idled for the first 30 minutes.

Flat tappet cams in most applications are designed to cause the lifter to rotate. This rotation converts what would have been a sliding motion in to a rolling motion without reducing oil entrainment velocity, and is essential in avoiding excessive wear. Where practical Kennelly Cams recommend running a flat tappet engine with the lifters or push-rods visible to observe that rotation is taking place. This can often be achieved by briefly running the engine with the rocker cover(s) or side plate removed, or a modified part fitted in place that allows visibility while still containing (most of) the oil.

The engine revs may be varied over 2000 rpm, e.g. between 2000 and 3000, to vary the load on the rings and other components that may also be running in at the same time.

During this time the engine should be checked for fluid leaks and the temperature closely monitored. Also listen for any unusual noises. It is safe to shut the engine down at any stage, but upon restart the engine must be returned to 2000+ rpm until it has done a total of 30 minutes running.

The idle speed may now be set at the normal rpm, and tappet settings or lash should be checked.

The engine should not be run over 60% of the normal redline until the correct valve springs have been fitted, and the oil and oil filter changed. Kennelly Cams recommend this is done before 500km is traveled.