Last night I finished putting together my first 350 (stroked to 383, injectors swapped to carb, dist swapped to HEI), and it started immediately, no problems.
But during the break in (running engine at variable RPM for 25 minutes) I noticed that once I apply a little bit of throttle, and bring the RPMs higher than idle (RPM gauge isn't working yet so I'm not sure the exact RPMS), the engine (or something around the engine, I'm not sure yet) makes this pretty terribly loud "rattle" sound.
I've checked the oil and the oil looks very clean wiped onto a coffee filter.
I also have a video of it starting and revving up, the sound in question starts at 0:10. https://www.youtube.com/watch?v=jWQd70ex3q4
Could this be something as simple as timing related? Or does this sound closer to having something inside the installed incorrectly?