I have a number of older Williams diesel engines, pre-Williams Bachmann, that are being re-greased. On one set of FA1 diesels zinc pest was evident on two truck sideframes and two motor mounts. What is evident is that this is a specific metallurgical casting lot issue and not a general problem nor date of production dependent, with the exception of these FA1 diesels not zinc pest has been seen in the other diesel truck side frames or motor mounts, all engines were purchased 10 to 25 years ago.
I would recommend that Williams engines be checked for this zinc pest issue, to check the motor mounts the shell must be removed and the can motor must be removed from the truck. Since the truck is removed the backside(s) of the side frame(s) are easily checked.