An agreement to allow modified American stock production engines to enter the 1979 Indianapolis 500 and to limit manifold pressure on turbocharges engines participating in all champtionship car events conducted by the U.S. Auto Club was announced todya.

This change means that assemblyline engines no bigger than those found in many passenger care may be used to power the race cars in the million-dollar chase.

USAC President Dick Kign said the moves will lead to more competitive racing at a lower cost. The agreement comes after a group of unhappy championship-car owners broke away from USAC to form a group known as Championship Auto Racing Teams (CAR).

CART, which includes owners of many of 1978's top cars on the USAC circuit such at A. J. Foyt, Dan Gurney and Roger Penske, has been sanctioned by the Sports Car Club of America and has said it will run its own events.

Asked whether the split in the championship ranks expedited the stock block approval, King replied, "It's been talked about since the early 1970s."

Joe Cloutier, president of Indianapolis Motor Speedway, emphasized that while the use of the stock block engine will become a realtiy at the speedway next year, he did not rule out continued popularity of the exotic turbo-charged engines that have dominated USAC championship races the past decade.

"In the past, we equated everything with the four-cylinder Offenhauser engine," Cloutier said. "Now we have the eight-cylinder Cosworth. We plan to equate such engines for next year with the stock-production engines."

Stock block engines have been used at the Speedway in the past, although with only insignificant success compared with the exotic engines.