Two major cable television system operators have agreed to acquire the cable systems of the former Storer Communications for about $1.55 billion, the companies announced Sunday.

The planned buyout by Comcast Corp. and Tele-Communications Inc. comes months after a larger consortium that included the two companies dropped a proposal to pay about $2.9 billion for SCI Holdings, the company created when Storer was taken private by the investment firm Kohlberg, Kravis & Roberts in a $2.5 billion leveraged buyout in 1985.SCI owns and operates cable television systems serving about 1.48 million subscribers in 12 states in the East and South. The company sold its six television stations last year for about $1.4 billion.

The companies did not provide details of the proposed acquisition in a news release, and telephone calls Sunday to people at Comcast headquarters in Bala Cynwyd, Pa. and Tele-Communications headquarters in Denver were unanswered. SCI offices in Miami were closed Sunday.

SCI did state that it estimated the purchase price would mean a payment of between $4 and $4.50 for each outstanding warrant of SCI.

Comcast operates cable systems serving about 1.35 million subscribers plus a number of Muzak franchises. The company also owns American Cellular Network Corp., which operates cellular telephone systems in New Jersey, Delaware and Maryland.

Comcast posted a net loss of $9.4 million in its 1987 fiscal year, compared with a 1986 profit of $1 million, or 3 cents a share, due to the costs of financing several acquisitions and to accounting factors. Revenue rose to $309.2 million from $130.8 million.

Tele-Communications owns or controls cable systems serving about six million subscribers, according to industry estimates. It also owns a 52 percent stake in the operations of the newly merged United Artists Entertainment Co., which has interests in cable television and movie theaters.

Tele-Communications posted a profit of $5.6 million, or 4 cents a share, in its 1987 fiscal year, down from $72.3 million, or 48 cents a share, the previous year. Its revenue rose to $1.7 billion from $645.7 million.