We get frequent enquires from customers who have modified and uprated engines fitted to their cars which have suffered from the inevitable valve train and specificaly rocker arm failure.
This problem seems to affect generaly TVR and other vehicles fitted with high lift camshafts.
Greater valve lift results in additional valve stem and guide side loading due to the greater angularity required by the valve train components. This causes wear on those components and increases friction.
It seems most are prepared to spend good money, time and effort on installing or increasing capacity, fitting ported heads etc without considering the less than adequate STD rocker arms.
The OEM Rover Rocker arms ( £640 + ) per set were designed to operate @ 5250 max rpm. When this rpm level is increased then the rocker arm is subject to stresses beyond the manufacturers design.
In time the inevitable will occur and can lead to more difficult and expensive problems to rectify.
This type of failure should not occur with a mild cam upgrade but where the engine is being built to perform for increased power, competition or heavy duty applications, roller rockers are the recommended alternative.
As newly appointed UK and European Distributors for Yella Terra, and since we are running a sales promotion on these, this maybe a good time to consider upgrading your rocker arms to the YT6000 replacements.
For competition applications consider the full cradle, solid ground shaft, needle roller rocker conversion system.
These reduce friction as well as shaft deflection and allow the whole rocker assembly to accurately open and close the valves with the highest degree of precision.
Picture courtesey of The Flying Welshman aka Doctor Dave D.
Vehicle 5.0 Litre TVR engined LR Defender.