John Curran will play a crucial role in Saturday's third try at the 70th running of the Indianapolis 500. Never heard of him? That's because he doesn't race cars, hawk motor oil on TV or fix fancy carburetors. This man predicts the weather.

Last weekend, Curran, the chief forecaster at the local National Weather Service office, was so wrong he went out several days later and gave a pint of his blood to a blood bank in a well-publicized act of contrition.

"It was the only way I could think to redeem myself," he said today.

Well, there's one other way. If he's right this weekend, the sun will shine Saturday at noon (EDT) on the 33 cars and estimated 250,000 spectators who have waited for what has become the world's longest car race. ABC-TV has waited, too, and will again attempt to show the first live network telecast of the race, beginning at 11 a.m. (WJLA-TV-7).

There is a 20 percent chance of widely scattered thunderstorms in mid- to late afternoon, Curran said.

"A typical race day forecast," he called it. "It's a completely different type of weather pattern than last weekend's. This will come and go. That one stayed."

He added a postscript: "This is no guarantee."

Last weekend, he said the rain would hold off until late Sunday, well after the race was supposed to be over. It rained all day. When it didn't stop the next day, the 500 was postponed, creating the longest delay in Indy history.

So, today, the talk in the long, concrete garages by the quiet track was about "windows." Not the ones you see through, but the ones the clouds make when they break up in the sky.

"We need a big, big window for this race," said former winner Tom Sneva, squinting into the comforting early-afternoon sun. "Give us five or six hours. That's what we need."

Sneva, the 1983 winner here, and Gary Bettenhausen, a local boy whose best finish was third in 1980, had been tinkering with Bettenhausen's car, tucked inside one of the scores of well-watched garages. They looked like two neighbors fiddling with a '72 Chevy in the driveway.

These were two of the 24 drivers who took their cars out for the 30-minute morning practice that created the only controversy here since the rain ended.

Speedway officials allowed a short workout for the drivers, but placed a 120-mph speed limit on it, almost 100 mph slower than the cars will travel Saturday. Some drivers said running at such relatively slow speeds was like not running at all, and criticized the decision.

"I felt like I was crawling," said Michael Andretti, who added that he was "bored to tears" by the week he just spent here, in a motel, killing time.

Andretti, who will race from the outside of the first row, took a few spins on the 2 1/2-mile oval track to check an oil leak. Others said they wanted to check the track and returned calling it "green," as in "when the race first starts, it'll be real slippery," said Al Unser Jr.

That's not because of any rain, but because the track hasn't been used in so long.

Pole-sitter Rick Mears and second-row starter Al Unser Sr. were two of the nine who didn't even go out.

"Every mile you put on the car might be the mile you need at the end of the day," said Roger Penske, who owns their cars.

Danny Sullivan, last year's winner, wouldn't have driven if he hadn't had to check the car radio, Penske said.

Sullivan will carry an ABC camera in his car, and the camera has been causing some static on his radio.

"It's kind of silly, but what can you do?" Sullivan said of his test drive.

Sneva was one of a couple drivers who may have gone over the speed limit today. Race officials had the black flag ready, which is racing's equivalent of the umpire's thumb, but never used it -- officially, anyway.

"They sort of held it up and shook it at me," Sneva said, smiling.

"I should have had my Escort [radar warning device] with me," said Tony Bettenhausen, Gary's younger brother. "They had about five speed traps set up out there."

It's hard to convince these people to go slow. This is the fastest field in auto racing history, led by Mears' record 216.828-mph qualifying speed. The 33 starters averaged 210.358 mph.

It was some feat just to have them wait five days to try to race again. Yet, even though the crowd is not expected to approach last Sunday's estimated 400,000, waiting was a wise choice, some drivers said.

"I was getting concerned with everybody's mental tiredness," said Josele Garza, whose car was sitting on airjacks in the pits when it was slammed into by another car in an accident during practice a week ago.

"Everybody was so worn out from [waiting] Sunday and Monday, and I don't think we'd have been as sharp as we should be if we had run Tuesday."

So, for the third time in seven days, the race is about to begin. If you think the drivers feel the heat, how about the weather forecasters?

"There's a lot of pressure on us this time of year," Curran said. "We're getting calls from everywhere in the country. A guy called from California this morning asking if he should come, saying it will cost him $2,000. We told him we can't make that decision for him. We just give him the forecast."

So what did this fellow do? Curran was asked.

"I think he decided to go ahead and come."