Would a loose wrist pin sound like a very noisy valve? .
Can't say, but from my experience a new noise is not a good thing.
our '19 is a thoroughly pooped out car which amazingly still has good compression and am not inclined to remedy the clanks and clonks it makes just yet. I have two cylinders which make a double "muffled clop" sound, and am convinced it is loose wrist pins. Also still has CI pistons and their noise (all 4) is distinctly different than a rod or wrist pin.
All rods are adjusted perfectly and stay put at 0.0015" after a couple of adjustments (car had no shims and I filed caps to take a very short shim pack...took 2 adjustments to get complete bearing surface and for rods to stop "moving"). I would think that a wrist pin would not have a sharp tap like a valve with too much lash.
Wrist pin noise is usually louder when cold and quiets down some when the engine heats up. It also usually goes away or gets quieter when the spark is retarded. At least that has been my experience in the past.
I always thought my T ran so quiet it was amazing for a car that old. Well a few weeks ago I had it out for a cruise and that what the hell this this is making noises I never heard before. I slowed down and sped up listening real close to figure it out. Then I realized I had my hearing aid for the first time driving. Turned it off and it sounds super, problem solved