Just started 350/290hp crate motor have ?'s

[Greubin]

UPDATE: The stumbling turned out to be a defective HEI distributor. Replaced distributor and engine now runs fine..BUT - unfortunately the engine has developed a knock at idle up to 1500 rpm. I've probed the engine with a stethoscope and these are a list of the things I know are not related to the knocking sound.
-valve lash adjustment
-fuel pump
-flexplate
-transmission
-alternator and power steering pump


The sound is loudest near the top of the bell housing, which I thought would be a cracked flexplate - but that's not it - I went so far as to replace the flexplate just for good measure. Listening with a stethoscope, the bottom end sounds, rocker covers and accessories sound tight. It must be related to either a main or rod bearing..but not sure. For warranty work, I have to take it to a GM dealer for evaluation, but I hate to think what they'll charge me for a diagnostic.


Any suggestions?

Previously -
Started up fine, did the 2000 / 20min break-in. Have one problem, the engine won't idle below about 1500rpm. I installed an HEI distributor, but I'm running the same plugs off my old engine, as they have about 1000mi on them( regapped to .045" for HEI ). The engine surges below 1500 rpm, and takes some foot work to keep it running at 1000-1500rpm. At 2000rpm, it runs steady.

Any ideas? I'm gonna double check the plugs and make sure they're the correct plug for HEI.

The other thing is the oil pres. seems high during the break-in - it was just below the H mark on the pressure gauge, even after engine was up to operating temperature.

Everything else looks okay, and no leaks.