Picture this: a bustling car wash in Morrisville, Pa., on a summer day in 1967. A business executive arrives to have his new Cadillac washed and waxed.

As his car is pulled inside, it is rammed from behind by a vehicle that becomes disengaged from the car-wash track. Observing this, the establishment's owner hurls himself into the soap and spray to separate the cars.

In his haste, the owner's foot becomes lodged in a conveyor belt that drags him through hot wax, rinse and 1,200-mph blowers. Two employes who do not speak English do not understand his pleas to activate an emergency-stop switch.

Finally, the Cadillac owner flicks the switch. "You don't need this," he says to the shaken victim, and persuades him to accept a job with his Trenton, N.J., brokerage firm.

A clip from an upcoming made-for-TV movie? No, just a very important day in the life of Lou Guida, 51, a high school dropout from Jersey City and a former car-wash owner who has gone on to amass a net worth of more than $40 million and is a senior vice president of Merrill Lynch. He also has become perhaps the most prominent harness horse owner in America.

Tonight, Guida will send his outstanding horse, Nihilator, into the second division of Freestate Raceway's $272,470 Terrapin Stakes for 3-year-old pacers. Nihilator, syndicated by Guida for $19.2 million and trained by Billy Haughton, last year earned $1.36 million, ran a record-for-age 1:52 4/5 mile and was voted champion 2-year-old pacer.

Driven by William O'Donnell, he scored a three-length victory last Saturday over highly regarded 4-year-old Russ Lyn Scott at Freestate. The 3-to-10 favorite, Nihilator covered the mile in 1:55 1/5, winning his 14th race in 15 career starts. He will be heavily favored in the seven-horse field tonight.

The performance ended speculation that Nihilator was unsound when withdrawn from a Freestate race the previous week. But Guida and manager Bob Boni had said there was nothing to it before Nihilator won the Smullin.

"It was normal racehorse maintenance, and that happened to be a good time to do it," Boni said. "If it hadn't been Nihilator, there wouldn't have been a second thought . . . "

Guida approaches harness racing with compassion, calculation and keen public awareness. By ascending the corporate ladder, he has accrued a wealth of business knowledge and has applied it in managing his 35 horses.

At the same time, he has alienated members of the sport's hierarchy. In April, Guida announced that Nihilator would bypass Roosevelt Raceway's $300,000 Messenger Stakes, first leg of harness racing's Triple Crown. It was the equivalent of Spend a Buck forgoing the Preakness.

"I think what Spend a Buck did will shake the industry up and make it more competitive," Guida said.

"The Triple Crown people believe they have a birthright to success. Nobody does. In order to get the public out to see a great horse . . . the race tracks who want that horse have to earn it. The Triple Crown doesn't mean a damn thing anymore."

Guida is focusing on the $1 million Meadowlands Pace in July to match Nihilator against two other outstanding 3-year-olds: Dragon's Lair, who gave Nihilator his lone defeat, and Primus. Guida owns at least a part of each horse.

Guida has another ambition: to prove the stud value of Niatross, Nihilator's father, in whom Guida purchased a half-interest for a then-unheard-of amount of $4 million in 1979. One year later, he helped syndicate the horse for $10 million. Niatross had a world-record 1:49 1/5 mile and earned more than $2 million, winning 37 of 39 career starts. But his style was not smooth or graceful, and many believed his lack of fluidity would hinder his progeny.

Not Guida. He privately purchased 15 Niatross foals. One of them was Nihilator, whom Boni selected.

"I went into racing back in 1972 because I needed a tax shelter, and for the first three (losing) years, I got one," Guida said. "Now, I've got tax income. I've been very successful in the stock market, but the horse racing business, I'd have to say, we've dominated."