With an apparent sense of political timing, American Security Bank yesterday named well-known Republican economist Alan Greenspan, who is a member of Ronald Reagan's campaign policy council, to serve as the bank's consulting economist.

Greenspan has been a key adviser to former president Ford during this week's political brouhaha over Ford's possible run for the vice presidency, and was aslo chairman of the Council of Economic Advisers during Ford's tenure in the White House. Greenspun succeeds Arthur Okun, an outspoken Democratic liberal, who died in March. Okun served as the bank's consulting economist for more than 10 years.

"Obviosly our primary concern is economics, not politics," said a bank spokesman. "Greenspan is one of the best economists in the world today."

Greenspan is president of Townsend-Greenspan & Co., an economic consulting firm. He will provide both short-term and long-term economic advice to the bank.

Greenspan was selected by W. Jarvis Moody, chairman of American Security, the city's second largest bank. "We are very fortunate indeed to obtain the services of an economist of Dr. Greenspan's stature," Moody said.

"His track record in projecting the shifts and patterns in economic activity -- both domestically and internationally -- has been outstanding and, indeed, his advice and counsel should prove to be invaluable to our trust and Money Center operations, as well as our key commercial and international customers."

Bank officials would not reveal Greenspan's compensation and said they had not received any assurance that Greenspan would not take a job should the Republican Party wind up controlling the White House in January.

Greenspan, who has been a frequent critic of Carter administraiton economic policies, predicted in May that the economic downturn would be a "horrible one", comparable to the recession of the 1974-1975.