Hello All,
Upon starting up and during the warmup stage there is this tapping noise that is very irritating and disconcerting. I have tried using seafoam and went to a heavier oil, namely 10w-30 synthetic. The good news is, after ten or so minutes, the noise goes away. The noise seems to come from the upper part of the engine. Any suggestions?

Sounds like one or more of your hydraulic lifters is not being lifted with a cushion of oil. Once they get clogged, they cannot be unclogged and you will have to live with it.
It is not worth disassembling the engine to remove/replace the lifter. It does no damage, just noise. Heavyer oil is the opposite of what you should do, in my opinion, but 10W30 is not heavy.
You may have had lower oil pressure due to a faulty O ring on the pick up tube, and even that is not a fun fix if you have to lay on the floor.

Just drive it slowly until the noise goes away? I did that with my 6cyl Mazda MPV for over 40K miles without harm.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)

Sounds like the typical faulty oil pick seals that are allowing air to be sucked up into the oil supply to the top end. Remove the oil pan and reseal the oil pump pick up tube and it should stop the ticking noise that the lifters are making because they have air in them. I have done countless sets of these and it has fixed the tick noise every time, in fact one of my vendors sells a kit that has everything required to do this job and it's part number is "tick kit".

Mark

A "tick kit"? I love it! LOL

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)