I just finished rebuilding the engine. I installed a crankshaft Kit, replaced the oil pump, replaced a bad connector rod, replaced the ballancer shaft bearrings, new rings, & Honed the cylinder walls.

When i first started the engine it ran smooth idling at 1K RPM's after it warmed up it idled down to 500RPM's then loud tapping & or knocking noise came from the exaust camshaft carrier & exaust side of the timing chain housing.

It seems that the oil pressure is dropping to low to keep the lifters primed & the hydralic chain tensioner engaged.

Is it just the engine is tight & needs to be broken in?

Or do I need to replace the lifters as well as the tensioner, sprockets & chain?

I have a very similar problem Carl. After I put my newer engine (8K miles) in it makes a clicking sound after it warms up also. Not a sound though until the temp gauge reads about 190. If you do figure out what it is please reply back on here even if nobody helps on here or you can also check here on my thread for a possible solution:
http://www.j-body.org/forums/read.php?f=11&i=115868&t=115868

Did you check the timing chain for tolerances? Sure you didn't reverse the cam sprockets?
Does it sound like it's making the sound once per rotation, once per 4 rotations, or less?? I know it's hard to tell, but any info would be useful.