What is source of engine knock?

Owned car for 1, driven 12k miles. After head gasket replacement, engine has gradually developed engine knock. ON cold start up knock for 3-5 seconds, sounds like multiple bearing knock(dry start up), then mostly goes away. Restart of hot engine after setting 1 hr, engine knocks 2-3 seconds.
If engine is accelerated under load to 2500 rpm or so(auto trans), & then partially back out of throttle & let rpms 'float', sounds like a definite bearing clatter.
Oil pressure seems to be marginally within spec, idle oil pressure dropped to 10 psi at idle, approx 600 rpm(?) Slightly under normal operating temp; spec is 13 psi, 800 rpm, 176 degrees F. Pressure quickly goes over spec 43 psi, with rpm increase.
Have oil pan down, screen not blocked, can't detect excess play on #2, 3, 4 rods, very limited access to #1 rod. Being closest to oil pump, I wouldn't think #1 bearing would be failed.
IS there any procedure to check rod bearings?
Has all new timing belt idlers & tensioner, water pump, accessory belts & idlers.

Suggestions?
Thanks
David