Bill Littlejohn of Dothan, Ala., can be called, with no fear of overstatement an auto-racing fanatic. He is as diehard as any Sears battery, and then some.

His apartment is ornamented with souvenirs of the road; photos of magnificent men and their racing machines, posters of the tracks where they drive. He has taken more transparencies of famous drivers than most parents do of their children in a lifetime.

He subscribes to Car & Driver, Road & Truck, and other enthusiasts publications. If there is a racing magazine on a newsstand, chances are he has persued it. His idea of a dry martini is a glass of gin and just a hint of STP.

Littlejohn even has a record of racing sounds - roaring engines, whining tires, shifting gears. It provides perfect background for slide shows and between-race reveries, he says. Obviously, one man's noise is another man's music.

Little spent last weekend on the infield of the Daytona International Speedway, watching, listening to and celebrating the 24 Hours of Daytona.

He has been here for the premier endurance test of American racing every year since 1966, with the exception of 1974. There was no raise that year because of the national fuel shortage. In Littlejohn's book, it was not a very good year.

It is aficionados like this who make the 24 Hours a wild and unique scene: the ultimate slumber party for people fascinated by things that go room in the night.

Littlejohn and his wife, Jane, who had the choice of becoming a racing buff or a racing widow, drove from Dothan to their old hometown of Jacksonville, rented a motor-home with six friends, and drove the 90 miles south along Florida's east coast to Daytona.

Here they met up with another group of friends, who had hired their motor home in Tampa.

Littlejohn's former roommate, Jack Zinkan - a pit crewman in Satursday's prelim, a 100-mile radial Challenge race for small sedans running on street tires - had roped off a prime location for his encampment on the muddy, drab infield that is ringed by Daytona's 3.84-mile "road course." It was near the garages and pits, with good views of both the sharply-banked tri-oval and the flat, twisting road portion of the course.

Motor homes and other vehicles too large for the small passenger car and pedestrian tunnel that connects the infield to the outside world lined up Friday, like a wagon train with modern conveniences, for admission to the grounds. Gates opened Saturday at dawn.

Ern conveniences, for admission to the infield, the big vehicles are here for the weekend. There is no way for them to get out until the checkered flag comes down on the 24 Hours Sunday afternoon. Then it takes another.

Once across the track and onto the five or so hours to "break camp," as the seemingly endless line of homes-on-wheels slowly winds out onto Route 92 to start the long trek home.

Daytona is not one of Florida's more pleasant towns, despite a beautiful beach. It is characterized by fast-food joints, plastic architecture, topless lounges and tacky amusements along the boardwalk.

At this time of year it is not even warm. This is northern Florida, not balmy Miami. All week long the palm trees have been shivering in chilly gusts, silhouetted against a dreary, overcast sky.

Even the mayor of Daytona Beach could not keep up appearances, as the Chamber of Commerce would like. When he welcomed a crowd of about 40,000 to the start of the 24 Hours Saturday afternoon, he said: "To all our guests from around the world, welcome to sunny Daytona Beach . . . Please don't freeze to death in our sunshine."

Behind him, the scantily clad majorettes of a local high school band, who had kept their blood circulating by high-kicking and twirling with particular gusto, started to turn blue. During the invocation they looked to be praying for the minister to finish, so they could put their capes back on.

But all this was of little concern to the dauntless buffs on the infield. They are accustomed to the cold, since temperatures regularly plunge after sunset, and come prepare for the long night's journey into dawn: 12 hours of racing in the pitch black.

Bunked out in tents, sleeping bags, cars, station wagons, pickup trucks, vans, campers, or the most elaborate mobile homes, they keep the party going, just as drivers and crews keep the cars running.

Away from their temporary headquarters, the spectators bundle in blankets, ponchos, heavy coats, scarves, ski hats and gloves. And they consume plenty of anti-freeze.

This is, curiously, not a heavy drug scene, but there is enough alcohol to turn the armies of the night into navies . . . "good ole boys drinking whiskey and rye" . . . beer flowing from bottles, cans, kegs and fully-equipped taps.

Racing fans know how to make the best out of roughing it. The infield, where admission is $15 per person for the weekend, is much more densely populated than the more expensive and sparsely people grandstands. And the festivities, like the smudge pots with their pervasive scent of kerosenen never run out of fuel.

The variety of life styles is astonishing. There are the simple folk who grill hot dogs or munch bread and cheese around campfires, and others who live it up.

One group of 40 from Orlando, for instance, paid $25 apiece to a group leader experienced at racing outings.He arrived at dawn Saturday to set up camp, complete with portable toilet and huge, wood-burning cooker. When he was ready, he hoisted a red, whiet and blue-striped flag with his initials on it to signal his conferes that the chuck wagon was open.

His menu was planned from Saturday lunch through Sunday's farewell cocktails. A sample meal: crab meat cocktail with chablis, baked ham and beans, corn on the cob and as much beer and sangria as one could drink.

Strange but undeniably interesting characters also roam the infield, mixing amiably with the hirsute, silver racing-jacket-clad Littlejohns of the world. Among this year's stars were a wild man with a Mohawk haircut, who periodically let out unprovoked rebel yells, and a self-appointed "Chicken Man," wandering around in a grotesquely life-like mask, dragging a rubber chicken with one of its drumsticks tied to a tin roasting pan.

Oh, well, conformity is not required here.

At night, the infield is almost surrealistic. The most enthusiastic race watchers stay up, clinging to the fence, as the cars keep streaking around like deep-voiced lightning bugs, or come into the pits for refueling, tire and driver changes, or drastically paced repairs.

The pits have their own assortment of aromas, sights and sounds - gas and oil mixed with mud and sweat, clanking wrenches, whispers of strategy and anxiety, and the verbal shorthand of crews and drivers experienced and working together in the interests of beating time. It is remarkable to watch a weary crew change four times in 40 seconds.

And even when most spectators are asleep, or otherwise engaged in their tents and motor homes, the speedway is never still.

As the smudge pots and campfires lend a dim, smoky glow to the night, the public address announcer cuts through the darkness, blaring a running account of the race. And there are the unmistableable sound effects of this sport, the melody of automibiles straining at high speeds thatBill Littlejohn finds both exhilarating and soothing.