What could cause burned valves in an overhauled engine?

Burned valves in an overhauled engine can occur due to several factors related to the engine's assembly and tuning. When considering valve lash, it is crucial to understand that it refers to the clearance between the end of the rocker arm and the valve stem. If this clearance is not set correctly, it can lead to improper valve operation. A valve that does not fully close may not get sufficient cooling from the intake or exhaust flow, ultimately causing the valve to overheat and become burnt.

Moreover, the valve seat width also plays a significant role. If the valve seat width is not correct, it can lead to improper contact with the valve, creating hotspots that can lead to burning. A valve seat that is too wide may not provide adequate sealing, while a seat that is too narrow won't allow for sufficient heat dissipation.

Both incorrect valve lash and improper valve seat width can contribute to the onset of burned valves, making the combination of these two factors a valid reason for such damage in an overhauled engine. Understanding these relationships is critical for anyone working on engine overhauls to ensure the longevity and proper function of the components.