knocking, cold and under load

Couldn't it just be detenation? Whats your timing at and what fuel are you running? Just trying to think of better things then a spun bearing.

Just thought maybe you brought the timing up a good amount and never put 93 in or something of th sort. Doesnt sound like that is the case though.

the sound would be the rod hitting the crank every time it moves toward where the potentially spun or worn bearing is supposed to be. Rods typically "float" on a film of oil. Without enough oil-pressure in that spot the rod is making metallic contact with the bearing and/or crank. The rod hasn't broken or the engine wouldn't run.

There's no way to know how long you can run the engine in that condition before it ****s on itself. If you're going to junk it, then no big deal, but if you'll rebuild with that block you should stop driving right away. If you'll continue to drive it, keep the RPM low and stay light on the throttle, ensure that you have 'ok' oil pressure and it might/probably will last a couple thousand miles in that condition. However, it might just chew up the bearing/rod/crank and send metal all throughout the rotating assembly which will likely cause the motor to fail and seize up the next time you drive it. If you put the engine under hard loads it won't last long for sure.

Oh, and in my last post, I didn't mean to reference fuel pressure, oil pressure is what I meant.

Chris

Oh, and to add a little more, the reason that I think it knocks cold and not hot is because as the engine warms up, thermal expansion causes the tolerances to tighten which brings up oil pressure and that helps to buffer the rod in question.

If it's just a ticking sound, it could just be your valve train (pushrod, lifter, a rocker that needs adjusting or replacement)... but you said it was like a mallet hitting the block, and that would indicate something more serious.