It is possible for the timing chain to have so much slop that it hits the cover. Usually if it is excessively loose you will have other problems such as hard starting from little or no cranking vacuum and lack of performance. Should be able to find the source of the sound using a long screwdriver or, better yet, a mechanics stethoscope.
Note: if your wife has a stethoscope from her occupation she will not see the crossover use as reasonable.
TIRE & WHEEL SALES
Two 14" Aluminum wheels $195
Two 15" Aluminum wheels $215
Four 14" Aluminum wheels $370
Free Freight within lower 48
Steel and galvanized wheels available. Spare tires too.