Swapped a 2004 Silverado 4.8L LS engine into my 86 Chevy C10 short bed Squarebody truck. Idled it maybe 45 minutes and drove it a grand total of 3 blocks. Ran great back to the house. Pulled it into the driveway and shut it off. Next attempt to start the next day and it sounded like this...
Pretty sure the timing chain skipped just enough to cause the engine to blow all fuel out the exhaust on the compression stroke and smack valves on the pistons. I believe the 'grinding' sound is actually valves hitting the pistons. Note that the 'grinding' occurs when the rocker on cylinder 2 is moving.
Please post any other ideas. Thanks!