Four of this weekend's eight National Football League playoff games--Cleveland at the Los Angeles Raiders, New England at Miami, St. Louis at Green Bay and Tampa Bay at Dallas--will be blacked out on local television in those markets because the stadiums were not sold out in advance.

Jim Heffernan, the NFL's director of public relations, said he could recall no instance of a playoff game being blacked out locally since Congress enacted the NFL blackout law in 1973. That law has since expired, but it has become league policy not to black out the games on local television if they are sold out 72 hours before kickoff.

In Los Angeles, the Raiders, who moved this year from Oakland to the Los Angeles Coliseum, said there remained 30,000 unsold seats for today's 4 p.m. game with the Cleveland Browns. The Dolphins had 6,000 remaining tickets, the Packers 10,000 and the Cowboys 15,000.

Tex Schramm, president and general manager of the Cowboys, said he expected Texas Stadium to be sold out by game time, 4 p.m. Sunday. "Since it became evident that our game wasn't going to be televised, there has been a line halfway around the building," Schramm said. He said he does not believe the lagging ticket sales reflects a permanent decline in interest in NFL football.

"I'm convinced the interest is out there. It's more of a question of getting back into the routine," he said.

The Washington-Detroit game, the Pittsburgh-San Diego game, the New York Jets-Cincinnati game and the Minnesota-Atlanta game were sold out and will be telecast locally.