Although American-made cars scored surprisingly well in preliminary Transportation Department crash tests, imported subcompacts still showed low levels of occupant protection during the 35-mile-an-hour crashes, the DOT reported yesterday.

Crash tests of 20 cars indicated that front-seat occupants in 13 of them would die if the car were involved in such a collision.

Transportation Secretary Neil Goldschmidt told reporters at a press conference that he was "particularly encouraged by the showing of such small cars as the Chevrolet Citation and Chevette, the Plymouth Horizon and the Ford Mustang."

He said the domestic cars' structures held up and their safety-belt restraint systems performed so well that the tests were "a clear indication that it is possible to build safer small cars."

The preliminary results cover 20 different 1979 models representing 65 percent of all U.S. sales. The remainder of the 1979 models still are being tested, and those results are expected later this year.

Dummies are used in the tests of how well cars hold up in crashes. More than half the cars tested wouldn't protect front seat occupants from fatal injury in a 35-mph crash.

Specifically the tests determine:

How well the windshield holds up, keeping occupants in the passenger compartment during a crash and preventing vehicle parts from smashing into it.

How well the entire fuel system holds up during a crash, preventing rupture of the fuel tank and or leakage of fuel.

National Highway Traffic Safety Administrator Joan Claybrook said she was disappointed that none of the imported cars tested did well in occupant protection.

"The preliminary findings from these tests indicate there are substantial differences in the degree of crash protection that manufacturers build into their cars." she said.

In the category of occupant protection, the Datsun 210, Volkswagen Rabbit, Plymouth Champ, Mercury Bobcat, Toyota Celica, Pontiac Firebird, Plymouth Volare, Ford Fairmont, Chevrolet Impala, Oldsmobile 98, Mercury Marquis, Chrysler LeBaron andDodge St. Regis all failed to meet government safety standards.

Although those standards are set for 30-mph crashes, the government decided to perform the tests at 35 mph to see how well the cars would do at higher speeds.

The Volswagen Rabbit, Oldsmobile Cutlass Supreme, Pontiac Firebird, Oldsmobile 98 and Chrysler LeBaron failed to meet federal standards for resisting fuel leaks.

In one surprise, the Ford Pinto, long plagued by problems with fueltank exposure during rear-impact crashes, passed the fuel-leak test in both front and rear impact accidents.

Only the Chevrolet Chevette and the Oldsmobile Cutlass Supreme failed the windshield-retention test.

Claybrook said the tests are the first step toward "giving consumers knowledge for comparison shopping." She said her agency is trying to develop a rating system that will show consumers quickly how well a car rates in safety features.

The only cars that tested that had perfect scores were the Plymouth Horizon, Chevrolet Citation and Dodge Magnum.

All models tested were 1979 models, except for the 1980 citation and American Motors Corp. Concord.