How much of the ZDDP did you add and to what weight oil? Might not be a coincidence, Dave. A friend of mine a few years ago added one of those products (think it may have been made by Lucas but not positive) to 10-40 weight oil. He said it was about a pint and it thinned his oil enough that his lifters started clicking and ticking. Right then, too.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end