The Federal Trade Commission staff wants to force the Ford Motor Co. to tell customers that there are defects in Pinto. Mustang, Bobcat and Capri cars that can cause premature engine wear.

The staff, in a document filed with the FTC's Bureau of Consumer Protection, contends there are camshaft and rocker arm defects in some 1.8 million of the cars built between 1974 and 1978. Those two parts, which open and close the engine valves, "have been failing as early as the first 163 miles of service."

Ford Declined immediate comment on the FTC document.

The "defect substantially affects the durability, reliability or performance of affected vehicles," resulting in "greater than normal" camshaft repair, the staff contended.

Although Ford began a program in July to repair the defect without charge if engine damage appears before 36 months or 36,000 miles have passed, the company isn't disclosing that program, the FTC staff said.

The staff also contended that Ford dealers "only reluctantly disclose that Ford may pay for the repairs," which cost about $226. Meanwhile, the staff said, many motorists are paying for other repairs that don't go to the problem.

The FTC staff contends that Ford knew of the problems by 1976 and told dealers to repair the cars in question. But, it said, many dealers were not doing the work because it costs them more to make the repair than the company was willing to pay.

In one case cited by the staff a customer went back to a dealer three times to repair the camshaft in less than 35,000 miles and is still faced with the prospect of a fourth repair job.

The FTC staff also attacked certain Ford television commericials featuring actor-comedian Bill Cosby, who shows the viewer a device he calls a "camshaft feeler," and tells them that the feeler finds "even the teeniest flaw in the shape" of the camshaft and "helps keep engines from running rough."

The Cosby commercials are "patently untrue," the staff contends.