I don't recall if these are solid or hydraulic lifters ( a read thru the FAQ's will tell you) - if they are solid lifters there is a certain amount of ticking. They could be out of adjustment.

If you have hydraulic lifters one may have gone flat sitting for those weeks. I had an old plymouth that would have a sticky lifter for about 5 minutes upon first start up of the day. Went on for years. You can buy oil additives that will free up lifters.

You can do the broom handle trick...hold a broom handle to your ear while the car is running and put the other end where you think the noise is...ie go down the length of the valve cover, put it on the water pump etc. Be careful...the engine is running.