First, would like to wish everyone a Happy New Year!!!

Now for the emergency, I am not sure what happened but felt something break on the engine a month ago, started rattling hard knocking sound in the engine. No idea what it is. Every time I start it now, it sounds horrible and loud rattling sound. At first I thought it was the header but there’s no smoke coming out of the engine bay. Someone suggested that it might be the pistons? Anybody have any ideas? If it is the pistons, what am I looking at as far as repair? Thanks guys!!

Dtownwolfpack.