I have a confession to make. More than 20 years ago, when I was in the Army, my old Chevy threw a rod. It would still run, but it sounded like someone was trying to wash pots and pans in an old Maytag.

A friend told me it was just a matter of time before the displaced rod split through the engine block. I had no idea what any of this meant, but I knew I'd have to replace the car--not easy with no cash for a down payment and nothing to trade in but the clattering Chevy.

On advice of this same friend, I replaced the car's engine oil with the thickest goo I could find, and succeeded in quieting the clanking down to a mere rumble. (Actually, the friend had suggested a mixture of sawdust and cup grease, but even desperate Army privates have scruples.)

Anyway, I managed to trade the car in on an Oldsmobile that was only in slightly better shape. The used-car dealer (he later told me) thought the feeder line that supplies oil to the valve tappets was clogged, a noisy problem but an easy one to fix. He also told me that he would give me credit for a $200 trade-in, though we both knew the $200 would be added to the price of the Olds. The last time I talked to him, weeks after the trade, he wanted to know how I had gotten the Chevy to his lot. He hadn't been able to move it since, he said.

Yes, there's a point to this confession. It is this: suppose it had been the Olds with the thrown piston rod. Should it have been illegal for the dealer to doctor the engine and sell the car to me as though it was in pretty good shape? I might have been stupid enough--or a clever enough mechanic --to buy the car even knowing about the rod, but certainly not at the price he was asking. But shouldn't he have told me about the problem?

America's used-car dealers don't think so. And neither does the Congress. Just last week, they voted to veto a proposed Federal Trade Commission rule that would have required used-car dealers to disclose the known major defects of the cars they sell.

The rule would not have required the dealers to inspect the cars for defects: only to disclose the ones they knew about, to tell customers the truth about their merchandise.

Opponents of the rule, which, without a congressional veto, would have assumed the force of law, said it was unfair. The National Automobile Dealers Association said it would have imposed unnecessary paperwork and increased automobile prices, further damaging an industry already in deep recession.

The paperwork would have amounted to a disclosure of warranty rights and a one-page sticker listing the car's major components--brakes, engine, drive train, electrical system-- and a check mark indicating "OK," "Not OK," or "Don't Know" for each component.

The recession argument is no more convincing. True, new-car sales are hurting, but the market for used cars is doing very well. What is left is the dealers' contention--confession, really --that they would have to charge less for their cars if they told the truth about them.

The FTC proposal, 10 years in the making, was a lot tougher when it was first proposed. Originally, it would have required dealers to inspect the 12 major systems of a car and then reveal their condition. The watered-down version the Congress vetoed eliminated the inspection requirement and allowed dealers to sell cars "as is." But it would have required them to disclose problems they knew about.

Even that was too much for the dealers. They managed to persuade the Congress to their point of view through a clever education campaign that included contributions of some $825,000 to more than 200 members of Congress.

On May 18, the Senate voted 69 to 27 to kill the proposal; last week, the House sealed the veto by a 286-to-133 vote. Perhaps they justify their votes as a further effort to get government off our backs.

Rep. James J. Florio (D-N.J.), calling it "a sad day for consumers," said he was "embarrassed by the actions of Congress." Rep. Barbara Mikulski (D- Md.) observed that "people should know if they are getting a car in reasonable condition or a four-wheel lemon."

Sen. Robert Packwood (R-Ore.) said the veto means that "in essence we are saying to the public we endorse shabby practices; we endorse cheats."

Just so. I'm ashamed of what I did back in 1960. I hope that at least a few members of Congress are ashamed of what they did this month.