I would not mess with it, unless the valves are bad.... If they are very loud.... or the engine misses because of bad valves..
do they sound like sewing machines? or just a slight tapping with the engine is cold? Also if the engine has high mileage, don't just have the valves reone, or it could burn oil, because of a mismatch between worn rings and new valves....
Don't try to adjust them if you have no experience and you could set the clearance and lash too tight...
too loose is better than too tight..
Good luck..
