ritcheyvs
Veteran Member
You need to read the specs. Some are spec'ed for cold and some for hot. When spec'ed for a cold (ambient) the adjustment spec value allows for thermal expansion of a hot engine.
Depending on the design (e.g. push-rod vs overhead cam) and materials in the valve train, valves could get "tighter" or "looser" as the engine warms up. I know the overhead cam design in my old Mercedes cars got looser when hot. For a push-rod engine (like Kioti) it would depend mainly on the thermal coefficient of expansion of the push-rods vs the block and head. Back in the day (as I vaguely recall) most valves were adjusted hot. Recently, I only recall seeing specs for cold valve adjustments, probably practical because of better manufacturing and material consistency. Valves that are too lose will be noisy and may accelerate wear (not the end of the world) but valves that are too tight could burn a valve seat or worse.
In my experience with the Mercedes overhead cam engine, valve adjustment was not predictable; some got loser and some got tighter. That adjustment was spec'ed for every 15K miles but didn't always get done.
Depending on the design (e.g. push-rod vs overhead cam) and materials in the valve train, valves could get "tighter" or "looser" as the engine warms up. I know the overhead cam design in my old Mercedes cars got looser when hot. For a push-rod engine (like Kioti) it would depend mainly on the thermal coefficient of expansion of the push-rods vs the block and head. Back in the day (as I vaguely recall) most valves were adjusted hot. Recently, I only recall seeing specs for cold valve adjustments, probably practical because of better manufacturing and material consistency. Valves that are too lose will be noisy and may accelerate wear (not the end of the world) but valves that are too tight could burn a valve seat or worse.
In my experience with the Mercedes overhead cam engine, valve adjustment was not predictable; some got loser and some got tighter. That adjustment was spec'ed for every 15K miles but didn't always get done.