Toyota Repair: Knocking noise, gasket leaks, head gasket

Question
About two months ago I replaced the head gasket on my 91 toyota cressida.  It was a tough job but the overheating problem appears fixed.  The only problem we had was that we could not get the harmonic balancer tightened to 185psi (we got it to about 140psi).  Just a day ago I noticed a knocking noise that appears to be lower in the engine or possibly in the transmission.  It is much louder in the morning especially when the car is cold.  It is much louder when the car is in gear and foot is on the brake or the parking brake is on.  Once the car warms up the sound disappears.  It sound like a helicopter inside the car.  Once you are driving the noise also goes away.  Any help would be greatly appreciated.  Shawn

Answer
Possibly a piston or connecting rod wristpin noise, typically the noise will go away after engine warm up because of the expansion of the internal parts.
I tend to think that it is a worn piston, when the head gasket leaks coolant into one of the cylinders it will wash some of the oil away and there is not enough lubrication of the cylinder wall and there will be excessive wear and possible piston failure.