"Hot smell"

The 2000 Accord I had to replace the head on a while back has a "hot
motor smell" to it. It's kind of like when you run a motor real hard for
a while. Sometimes it has a slight coolant odor to it.

It has no leaks of any fluids. It runs like a Swiss watch. Has all the
pep and vigor you could want. The oil is fine in quantity and color. The
coolant level is fine. I'm stumped.

After I replaced the head I Gunk'd the motor down. Of course that stunk
for a while but went away. I even replaced the exhaust manifold heat
shield thinking maybe the insulation on the under side of it had
absorbed some Gunk. I remember we had a question about which side was up
with the head gasket. What symptoms would an upside down head gasket show?

It's definitely coming from the motor. It's not a strong odor but it is
definitely there. Any ideas out there?

TIA

Nasty