The name Opinca, Opincar, or Opincaru still exist in Romania. In fact, the word "opinca" means "traditional shoe worn by a Romanian peasant" and the word "opincar" means "a person who makes this special shoe"; "opincaru" means "the maker of the traditional Romanian shoe". Way back in history (probably hundreds of years...), your ancestors must have originally been shoemakers of this kind of Romanian traditional shoe.
You should contact Romanians who actually live in Romania and can get in touch with families with this name. Unfortunately, not many Romanians check this page unless they live abroad. Most Romanian-speaking Romanians wouldn't post here unless they spoker very good English. If you had a chance to go to Romania and go through information there, it would probably be easier for you. If you actually searched the archives, you could probably come across your ancestors if they were actually registered.
I am a Romanian who immigrated to Canada 20 years ago when I was 13 years old. I can still speak Romanian and I still visit there.
I am answering this message because I have looked at some of the queries that still remain unanswered. I came to the conclusion that one of the reasons for this silence may be that there is no corresponding site IN ROMANIAN for regular Romanians WHO ACTUALLY LIVE IN ROMANIA to answer these searches.
Just a thought... :-) Good luck with your search!