Through the many years of working with the Honda V-4 engine, the main problem causing cam and rocker arm failure is the lack of a good oil supply
to the heads.

Since the beginning Honda has made many upgrades to the materials, hardness, etc., but the problem can still occur at any time. The stock top-end oiling system is low pressure, low volume and unfiltered. One thing that most people overlook is that the top-end is getting it's oil supply from the low pressure side of the oil pump that also feeds the
transmission.

To build the pressure to an acceptable level the oil passes through a nozzle with an .080" hole which equals less than 25% of the ID of the metal hoses it feeds. If the oil is not changed regularly, debris can also be passed through to the heads which can cause cam journal gouging. Also, when the engine is at idle the pressure can sometimes drop below 8 psi meaning that sustained idle time can cause wear that progressively gets worse.

The stock top-end oil system has no provision to stop back-flow, which means when the engine is not running the lines that feed the heads drain back into the crankcase causing a dry start-up situation in the heads. Proper valve clearances are also important because the stock oil system feeds no substantial volume, tight valves can actually wipe the oil from
the lobes and rocker surfaces causing even more wear or cam pitting.

This is why Honda increased the clearance spec from .004" to .006". When the engine is at running temp., valve clearance is reduced as much as .003" from part expansion. The entire surface of the cam only gets lubricated at the point on the heel of the cam where you have clearance. There are even occurrences where an engine and cams will be fine for 30K or more miles then all of the sudden cams fail. This can be caused by the last valve adjustment being too tight, or a weakened oil pump. An oil system that is barely good enough to begin with, can cause problems as the pump loses it's full pressure from wear.