A sign outside a service station on Route 92, the main drag running west from the beach out to Daytona International Speedway, reads: "Welcome race drivers and fans. Two pro mechanics on duty, 7 a.m. - 11 p.m. daily."

This notice may be of interest to a handful of "have nots" among the record field of 84 entries for the 24 Hours of Daytona, which starts today at 4:30 p.m. It is of no concern to the favorites in this longest, most arduous endurance test of American racing.

Most of the big-name drivers from the U.S. and 14 foreign countries have come here as part of lavishly financed and equipped teams, either factory-backed or heavily supported by fiercely competitive manufacturers - especially Porsche, the acknowledged leader in this gruelling type of racing.

Their entourages include drivers carefully teamed by temperament and physical size (the better to switch the individually molded seats that contribute to driver comfort, important in a marathon race), plus experienced mechanics, pits crews and timers

They travel first cabin, with truckloads of extra engines, parts, tires and equipment. The crews that work busily, efficiently in their tin-roofed garage areas are well turned out in jumpsuits bearing a dizzying variety of logos - the names and trademarks of suppliers that have launched thousands of racing machines.

Instead of squishing through the ankle-deep mud that three days of rain have left in the pits, getting splattered like their poorer cousins, they do the splattering with pick-up trucks and smaller vehicles that chauffeur them wherever they want to go.

The motor homes that form their temporary headquarters are the most luxurious among the village of live-in vehicles encamped on the drab speedway infield. No modest campers, vans or station wagons for the heavy hitters. Their toilets flush, and their digs are plush.

Foremost among the "haves" is daper, urbane Peter Gregg, Harvard man and owner of a prosperous Porsche dealership in Jacksonville, Fla., the only man to win this 18-year-old test three times in a row: 1973-75-76. (There was no race in 1974 because of the energy crisis.)

Gregg's JMS Brumos Porsche Racing Team, which is fielding two turbocharged Porsche 935s, has 55 accredited members - though Gregg is the first to admit that some of them are as necessary as food stamps at San Souci "There are a few girl-friends in there," he said, "but most of the people have jobs."

Gregg, 37, had to buy credentials for 35 of his volunteers and camp-followers because Daytona allots only 10 "workers" credentials per car. "I'm sure we have the largest team for the race," he said, an Ivy League understatement.

Consider, for instance, the Interscope Racing Team that captured the pole position with a lap time of 2:00.152 for the 3.84-mile course (115.054 miles per hour) in another turbo Porsche 935, driven by Danny Ongais during Thursday's rain-slicked qualifying. It has only six regular members, although a third driver - respected California wheel-for-hire Milt Minter - was brought aboard to share the 24 Hours with the talented Ongais and owner Ted Field, a well-to-do 25 year-old from Newport Beach, Calif.

"We have a crew of only four, a team of six, but I like it that way," said Ongais, 35, a Hawaiian-born ex-motorcycle racer who was rookie of the year for Indy cars last year."We've been together three years, work well together, and have the makings of a first-rate team. It's close knit because everybody knows they're contributing."

So how could Gregg, who will share the wheel with Claude Ballot-Lena of France and California Brad Priselle, possibly utilize 55 bodies, even with two cars?

To the best of his recollection, he has five drivers, a dozen mechanics, 18 timers, scorers and signalers, six crewpersons for the team's three mobile homes, a doctor, two bus drivers to run a shuttle service between the pits, mobile homes and a hotel, one food service manager, two cooks and three team managers. The rest of the squadron, presumably, are girlfriends. Except for the lady with the doctor. She's his wife.

Best bet of the week is that even if Gregg wins the $17,500 first prize, from a total purse of $83,000 (plus $31,985 in manufactures' contingent awards), it will not come close to covering the Brumos team's expenses.

The "have nots"? There are a number of them here too, backing entries merely for the thrill of seeing if they can coax their cars and themselves through this Utimate test of man and machinery.

The man hauling a tire through the mud in a child's bright red wagon during Thursday's first night practice was one of them. Didn't he think he'd better change to wet tires in the persistent dizzle? he was asked. "Ain't got any," he replied, slogging on undowned through the muck.

Venlo Wolfsohn, the well known Washington motorsports writer fondly remembers a man named Franklin Waltman, who one year drove his Morgan from his home in Long Island, unloaded a new set of tires from his trunk, put them on and was ready to race.

He napped for one hour in every four and drove the 24 Hours singlehanded. He finished, fulfilling a long-held dream, and wasn't last, either.

There are no soloists anymore, because the rules now stipulate a minimum of two drivers per car and a maximum of three. No one may drive more than four consecutive hours without taking at least an hour's rest, or a total of more than 14 hours.

There are still some rather quixotic entries, however, Dr. Ron Case, 38, of Lakeland, Fla., for example, has entered his own Porsche 911 and will co-drive with Dave Panaccione of Tampa, who is not likely to be confused with Jacky Ickx. The tiny photo of Case in the offical program is the kind you get by ducking behind the curtain in one of those shopping center booths. Four poses for a dollar.

If the independent entries are a kind of last American adventures, troupers personifying the pioneer spirit in the automotive age, many of the better drivers refer to them resentfully as "hotdogs."

They think the 'amateurs' present [WORDS ILLEGIBLE] an already dangerous business, since their speeds can be as much as 50 m.p.h. below that of the leaders.

This is particularly troublesome at night, and will be more so if weather forecasts calling for clearing on the weekend turn out to be incorrect. If the drizzle and mist that have hung drearily over the colorless speedway landscape through qualifying persist, drivers will be under even more pressure than usual to remain 100 percent alert and concentrating.

Bill Tuthill of the Society of Automotive Historians reckons there are three classic distances in auto racing: the one-mile measured straightaway, 500 miles, and 24 hours. He likens these to a shootout ("draw, bang-bang, and it's all over"), a battle ("several tense hours of driver concentration, crew expertise and no time for second guesses"), and a war.

"Something breaks," he said of the 24-hour tests of character and engineering that trace their origins to Brighton Beach, N.Y, in 1905, "you fix it. Something happens to the driver - you have another one ready. This is a race in which perseverance may be as rewarding as sheer power and speed when the long, long loed suddenly evaporates in a cloud of smoke."

Mechanics consider the 3.84-mile Daytona course a tough one for which to set up their cars because it incorporates some two miles of the speedway tri-oval, which is banked at 31 degrees, with a twisting but flat "road course" that includes two hairpins - one lefthander and one right. The transition from the steeply-banked to the perfectly level part of the course takes place within a quarter-mile.

The road portion requires 17 gear shifts, but then drivers accelerate all the way around until the approach to the first run, reaching speeds well over 200 m.p.h. on the final straightaway.

It is a dull course for drivers because it is so flat, with none of the hills and natural scenery that characterize LeMans, the most celebrated home of this essentially European style of racing.

The 24 Hours of Daytona has been called "the twice round-the-clock marathon to nowhere," but the cars that finish cover a great deal of ground in getting from the green flag to the checkered one.

The Porsche Carrera driven to a 21-lap victory last year by John Grave. Dave Helmick and Hurley Haywood - who teamed with Jacksonville neigbor Gregg for victories in 1973-75 and last year became the first team to win Daytona and LeMans the same year - averaged 108.801 m.p.h. and traveled 2,165 miles.

That is the equivalent of driving in one day and one night, from Florida to California.