The two new model cars on which Ford Motor Co. and Chrysler Corp. have staked their futures both failed a severe government crash safety test, the National Highway Traffic Safety Administration reported yesterday.

Ford Co.'s idential "world cars" -- sold as the Ford Escort and Mercury Lynx -- and Chrysler's twin "K cars" -- the Dodge Aries and Plymouth Reliant -- failed to protect passengers in a simulated head-on collision at 35 miles an hour, the government safety agency disclosed.

The test dummies. A real passenger in either car might have

The test dummies. A real passenger in either car might have died from head injuries after striking the dashboard.

Only a handful of cars have ever passed the NHTSA test, the most demanding crash standard set by the government. Federal regulations now require cars to protect occupants from injury in a collision at 30 mph. The standard will be raised to 35 mph for large cars in the 1982 model year and for small cars in 1985.

NHTSA has been measuring cars against the stiffer standard to show that it is possible to build a car that is safe and to dramatize the need for building safer small cars.

The Escort/Lynx "performed better than most other subcompacts in the 35 mph frontal barrier crash tests," the agency reported. "The driver was well protected" by the car's standard seatbelts and crash resistant steering column, the agency said.

For a front-seat passenger, however, the test produced "a borderline failure" on head injury protection. The dummy's head smacked the instrument panel.

A Ford spokesman criticized both the testing proceedure and the results for the Escort/Lynx. The test measures the impact of the dummy's head against the dash, he explained. If the dummy's head hits hits hard enough, it is considered dead, and the car a failure. The impact for the Escort/Lynx passenger was one-tenth of 1 percent over the limit, Ford officials said.

"We think the performance in the Escort is very, very good," he said, "but we think the test is flawed, its criteria are not valid in the real world."

The Chrysler K cars "showed relatively good structural and belt performance," NHTSA reported. "The driver was well protected by the belts and the very good steering column and steering wheel."

But the dummy in the passenger seat hit the K car's dashboard in two places, even though strapped in with the shoulder harness. "The severity of the impact was increased by the fact that the instrument panel was pushed rearward and upward during the crash, and by the fact that the edge of the instrument panel has a relatively rigid metal structure that is only marginally padded." The shoulder harness let the belt pull out more than it should have, the agency added.

A Chrysler spokesman said the test "is a stunt and has nothing to do with the current federal safety standards.

"Chrysler's 1981 cars, including the K car, passed all existing safety and emission tests," he said.

In a similar rear safety test in which a 4,000-pound wall is slammed into the back of the car, neither the Escort nor the Aries leaked fuel, NHTSA reported.

When the agency released its first 35 mph crash results last winter, every foreign car failed and only four American models passed. The survivors were the Chevrolet Citation and its sisters under the skin, the Pontiac Phoenix, Oldsmobile Omega and Buick Skylark; the Dodge Omni and Plymouth Horizon; Ford Mustang and Mercury Capri, and Dodge Magnum and Chrysler Cordoba.

In a second series of crashes reported in August, only the Chevrolet Citation and Fiat Strada got passing marks.

The Chrysler K cars and the Ford Escort/Lynx are the first 1981 models tested by the agency.

Detroit automakers have consistently opposed the crash testing program, objecting to them even when their cars passed, and their import competitors failed.

But some groups of car dealers have used the poor performance of the imports as a selling tool, and touted the safety of American cars. A group of Chevrolet dealers in the New York City area recently bought newspaper advertisements and billboards pointing out that none of the Japanese imports pased the tests, but the Chevrolet Citation did.