I had that some problem on my m42, started getting the chain slap, but if i rev above 3500 i would go away, but return up engine revving back down so i replaced the chain tensioner, and i installed mine all the way extended, noise got better could still hear it everyonce in a while, then it started pretty regular again so i installed some lucas oil stabilizer miracles happenend noise gone and on my merry way, wasnt merry very long about a month or so noise came back and this time it was pissed, would not go away and was like i never heard it, so off with the front cover, i think i can help you with that piece of aluminum i aint good sorry, i had so much chain slap that i finally ripped my chain tensioner out out of the front cover sending it into the cover to grind away, i just replaced my engine it was cheaper, i hope better luck for you but that chunk of aluminum doesnt look good, just dont want you to waste time and money on false hopes as i did, pull you front cover off before you go any further.