American Express Co. yesterday made a $230 to $250 million takeover proposal for Philadelphia Life Insurance Co., topping an earlier $170.6 million offer for the insurer by Tenneco, Inc.

A Philadelphia Life spokesman said the company's directors would meet shortly to review the offer. The American Express proposal involves a taxfree exchnage of shares of a new issue of American Express convertible preferred stock for all of the 10-15 million shares of Philadelphia Life.

On Aug. 25, the insurer signed an agreement in principle to merge with Tenneco. At that time, Tenneco held about 24 per cent of Philadelphia Life's stock.

Tenneco, a diversified industrial giant with oil, natural gas and manufacturing interests, declined to comment on the rival bid.

Tenneco had offered to exchange 0.22 shares of a new 7 per cent voting preference stock with no par value, but a $100 liquidation value, for each outstanding share of the insurance company. The preference stock would be unredeemable for 10 years, but would be subject to a sinking fund that would retire the issue by the end of the 20th year.

Philadelphia Life has more than 300,000 policyholders throughout the U.S., a spokesman said. The face value of its policies sold in the first half of 1977 increased by 5.5 per cent to $728,3 million from the same period a year earlier. Income from premiums during the first six months totaled $78.9 million, the spokesman said.

The insurer has sales division headquarters in San Francisco, Houston and Philadelphia, and is licensed to operate in all states except New York.

American Express offers worldwide travel-related services and also is involved in other insurance and international banking fields.