Knocks at Idle When Hot

^ Loose or worn drive belts. Tension and/or replace as necessary.
^ A/C Compressor or generator bearing. Replace as necessary.
^ Valve train. Replace pans as necessary.
^ Improper oil viscosity. Install proper viscosity oil for expected temperature.
^ Excessive piston pin clearance. Ream and install oversize pins. Or replace piston and pin.
^ Connecting rod alignment. Check and replace rods as necessary.
^ Insufficient piston to bore clearance. Hone bore and fit new piston.
^ Loose crankshaft balancer. Torque and/or replace worn parts.
^ Piston pin offset to wrong side. Install correct piston.