Four years ago, the Indianpolis Motor Speedway was declared unsafe at any speed greater than 185 miles per hour by two impressive witnesses.

"We're just pointing the cars now, not driving them," said A. J. Foyt.

"At 150 miles an hour, we had maybe seven seconds to react to something," said mario Andretti. "Now we have .8 of a second. It could be critical soon."

It could be critical now. Today the charges of USAC push their swift and delicate machines toward - and probably past - the 200-mile-per-hour during qualifications for the 500-mile race May 29. And the two leadfoots pushing the hardest are Foyt and Andretti.

Indy officials are pulling out all stops so someone officially breaks 200 today. They are doing that by eliminating something known in the trade as a "popoff valve," an automotive version of what cetain Washingtonians wouldlike to see on Andrew Young.

It came into being not long after the Foyt and Andretti protests, after Art Pollard died during a practice lap, after Salt Walther roasted before the 1973 race was 100 yards old and Swede Savage later was killed. Speeds decreased. Now the urge to challenge what the drivers call "the edge" has returned.

"The edge" is the often unknown point that separated gutsy driving from recklessness - and the Indy crowd is gambling that resurfacing a track otherwise unaltered since it opened in 1909 will allow once unimagined speeds without too much gore. With no gore, the Speedway becomes a cornfield.

In March, it became obvious that Johnny Rutherford's track records for one lap (199.071) and four-lap average (198.413) set in '73 would be in danger. Gordon Johncock sped 200.4 for one lap during tire tests.

Late Wednesday, Andretti became the first to exceed 200 during the annual May hype. He did it late in the afternoon and one-upped Foyt's earlier 199.956. Apparently, news of Andretti's 200.31 hit Foyt like a wrench, because less than 15 minutes later he was on the track again.

Foyt might well be the most intense competitor in all of sport; certainly he is the most versatile man in the history of high-speed bumper cars. He was two-tenths of a second slower than Andretti on Wednesday; he may not be today.

Whenever someone squeamish - or is it sane? - asks the all-important "why" of an Indy driver, say the articulate Dick Simon, the response usually is: "Because if I can't have a challenge, what is there to life?"

While in college, Simon began ski jumping. It was a nervy enough adventure - and especially so the time he was at the top of the takeoff area and a man with a flag in the landing area gave what Simon thought was the all-car sign.

Simon pushed off, and launched into exhilarating flight seconds later - only to discover a cleanup crew in exactly the spot he figured to land. Instantly, in mid-flight, he came up with a solution.

"There was another jump and landing are just to the right of the one I was on," Simon said, "so I adjusted my body in such a way that I landed on it. Yes, I pushed off of Jump A and landed on Jump B.

Clearly, such a man is not going to be satisfied with an ordinary job. Simon's was a steady trip through the minor leagues of racing to Indy - and the predictable divorce. Now a woman, Janet Guthrie, has earned her spurs by "kissing," as one report put it, the walls of Indy at more than 190 miles per hour.

To justify its existence as something other than as a profitable outlet for the folks who chase accidents and fire trucks, Indy officials insist the race acts as a testing ground for innovations that later become standard safety equipment on ordinary cars.

One of the those devices was said to be the rear-view mirror, supposedly first used by the winner of the first 500, Ray Harroun, so he could watch traffic behind him. Then Tony Hulman talked with Indianpolis newsman Wayne Fuson last year.

"I was spending some time with Ray not too long before he died," Hulman recalled. "I mentioned to him something about the rear view mirror on his car being the first one ever.

"He said to me, 'You know, nobody really ever-asked me about it, but honestly, between you and me, I couldn't see a damned thing in that mirror because of the vibrations of the car."

So most of the practical reasons for Indy and serious auto racing are pale. Except one. It does keep Bobby Unser off the streets.