Elizabeth Blalock Blackford, who had been a teacher in Virginia and West Virginia and a resident of the Baltimore area since the early 1930s, died April 6 of heart failure at Church Hospital. She was 86.

Mrs. Blackford, who lived on Weatherbee Road in Towson, taught chemistry at schools in Alexandria, Va., and Salem, W.Va., before her marriage to Chester Blackford. Mr. Blackford retired as a central office engineer for the Chesapeake & Potomac Telephone Co. before his death in 1977.

The former Elizabeth Blalock was a native of Culloden, Ga. She was reared in Jonesboro, Ga., and was a 1925 graduate of Agnes Scott College in Atlanta.

A brother, Dr. Alfred Blalock, professor emeritus of surgery at the Johns Hopkins medical school and co-developer of the Blue Baby operation, died in 1964. Another brother, Edgar Blalock of Jonesboro, who was long a Georgia legislator, survives her.

Other survivors include three sons, Chester Blackford of Cape Coral, Fla., George Blackford of Easton and Robert Blackford of Severna Park; one sister, Georgia Blalock of Jacksonville, Fla.; and four grandchildren.

No services were planned. The family suggested that memorial contributions to benefit the Alfred Blalock Chair could be made to the Fund for Johns Hopkins Medicine.