Thanks Jerry and Dave. This engine is in a 29 5 window coupe that I bought in Jan. The first thing I did to it was pull the cam gear drive out of it and I replaced it with a 2 row chain drive. It ran just fine until recently when the when the knock occured. I was just bewildered when I pulled those 2 rod caps because I've never seen anything like this in any engine. I'm 62 and thought I'd seen it all. Being disabled I was hoping I wouldn't have to pull the whole engine apart.
I'll pull the rest of the rod caps tomorrow and see if they are all alike, then start pulling the main caps. Thanks again