2 Vacuum Pumps destroyed timer Bushing Identified as the problem
http://www.mbca.org/forum/2013-12-29/why-are-these-vacuum-pumps-being-destroyed
However find out if any of your valves are bent first.
Another way to tell if you valves are damaged would be to remove the camshaft and do a leak back test. Or at least pressurize the cylinders with compressed air. If any valves are bent you are going to hear a lot of air hissing into the manifolds.