[weim55]

Good for you to pay the $$ and get an experienced set of eyes and ears on the problem. I've spent most of my working years as a mobile construction mechanic. It's always baffled me people will spend $$ like crazy throwing parts at a problem but refuse spend $$ toward experienced labor to diagnose a problem first.

You mention you thought the sound might have started after you worked on the crankshaft to balancer bolt issue. Plus the mechanic found the noise to be in that area. From the information above here's what I would do: remove water pump to have good visual and next the crank drive bolts and pulley. Water pump could be hitting the timing cover or crank pulley bolts too long. Fire the engine, if the noise still exists, remove the crank to balancer bolt and grab the balancer with both hands and see if it is loose on the crank. I know this sounds silly to some but if the crank snout-balancer is damaged you've chased the problem to here. Perfectly OK to run the engine for testing without the bolt if the balancer is tight. Fire the engine again, if the noise still exists shut down the engine and look very carefully with a good light 360 degrees on backside of the balancer for good clearance between the balancer and timing cover. Any witness marks of the backside of the balancer rubbing something. This is very tight even when everything is perfect. A junk China timing cover has me suspect as would a used or junk China balancer. When you installed the balancer bolt and snugged it up the balancer it might have fully seated to the crank and caused the noise to appear you are trying to chase. Likely you'll find the problem in the above paragraph. If not post and we can dig a little deeper.

Second, ask the previous owner if the engine was purchased as a crate long block. If so I wouldn't be so concerned with removing the engine for a teardown- inspect.

Steve weim55 Colorado