valve train noise or worse ?

Hi,

Can I bring another question to this forum ? I looked at the archives, but
found nothing similar for this noise pattern or situation. And I wonder what
a mechanic would say, given lash values are correct for most of the dealers.

My car has had valves tightened a bit too much, now they're at correct valve
lash. For a while, I hear too much noise coming from the cover. Valve lash
increases with temperature ( is it always so ? ) and seems lower in
frequency and much less noticeable when warm

It is loudest on a cold engine, and in the afternoon, with engine still
warm, is never that loud again. It also becomes very high in frequency when
cold when the throttle is released, after driving in low gear and low load,
the clatter increases just after release in volume and frequency, and
diminishes after about a second ...

Does the noise pattern, like after throttle release, point to something
worse ( low- high end or main bearing ) ? I thought they would make heavier
noise. There could have been oil issues in the past. Also, timing could have
been too early 4 degrees for a long time, or late 4 degrees for 1000 miles
now, giving more than normal bearing load ?

Now this valve train has a OHC, two rocker shafts and 12 valve rockers with
4 exhaust ones. The rockers are cast aluminium, with iron or steel adjuster
screws. I imagine it is not such a big deal to install new rockers and
shafts, and even a camshaft, and adjust valve lash again. But from where can
this noise come when valve lash is correct ? The car has 35 k miles and oil
was changed just at 33k5 miles. Is there something with aluminium rockers
and steel adjustment screws, which should not be overtightened ( they
tighten even further when hot ) ? They could have been.

Looking forward to any advice,

MTIA,

Carl