* Incorrect valve lash: Rocker arms are designed with a specific length and geometry to provide the correct valve lift and clearance (lash) when adjusted properly. Mixing them up will result in incorrect lash for some or all valves. This can cause:
* Poor valve timing: Valves may not open or close fully or at the correct time, leading to reduced power, rough running, and potentially valve damage.
* Valve float: At high RPM, valves might not close completely before the next piston stroke, leading to bent valves or piston-to-valve contact. This is a major engine failure.
* Burned valves: Incorrect lash can cause valves to stay open too long, leading to overheating and burning of the valve faces.
* Premature wear: Incorrect lash accelerates wear on cam lobes, lifters, and valve components.
* Rocker arm geometry issues: Even if the rocker arm lengths seem similar, there might be slight differences in the geometry that affect the valve's motion. This could lead to uneven valve lift or poor sealing.
* Interference: In extreme cases, incorrectly installed rocker arms might physically interfere with other components, leading to immediate damage.
In short, mixing up rocker arms is a serious mistake that can cause a wide range of problems, from difficult starting and poor performance to complete engine failure. It's crucial to meticulously mark or document the position of each rocker arm *before* disassembly and ensure they are reinstalled in their original location.
