Misadjusted valves will cause a rattling noise and late valve timing since the slack has to be taken up before they start to open. Late valve timing can also be caused by a stretched timing chain on those engines that use them. If you remember "L" for "loose", "late", and "low", loose valves cause late valve timing which increases low-end torque. Motorhome engines often use retarded valve timing to change the personality of the engine to provide greater torque for leaving stop signs. Once up to speed, that torque isn't as important when just cruising.
Late valve timing won't cause overheating. If the valves are adjusted too tightly, they will be prevented from sitting firmly on the seats when closed. That will reduce how effectively heat is transferred from the valve face to the cylinder head and into the cooling system. That will result in burned valves and a severe loss of compression.
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Wednesday, January 25th, 2012 AT 2:48 PM