How can i find out about my jewish heritage if my great-grandfather changed his

Question:

How can i find out about my jewish heritage if my great-grandfather changed his last name to a spanish name.?

My greatgrandpa came from Jerusalem and changed his name in Mexico than he migrated to Arizona. His last name was Haddad but changed it to a spanish name (Encinas).
I've checked out his record with the U.S census in 1930 through ancestry.com, but it said that his parents were Mexicans, however my grandfather recalls him being from Jerusalem. His memory is very vague, as he is 87 yrs old. I need to find out all the info I can because my grandpa is getting older. Thank you

Best Answer - Chosen by Asker: Where in Mexico? Look for records there may be a route. Did he immigrate, what do NARA files have?

Since you are jewish, then your mother is jewish, yes? There will be at least some historical records. Unless, were the ancestors conversos?