Most neighborhoods would know Charles Christ as the really big guy who is always tinkering around with that really small car. But in a Breinigsville neighborhood, he is the 389-pound guy who's always tinkering with the really small orange car that has all those No. 25s on the doors and hood.

''It's the Orange Bombastic Bug Killer,''' Christ said. ''Or, as one of my friends calls it, The Weed Whacker from Hell.' Being a two-stroke engine, it sounds like somebody with a chainsaw or Weed Whacker.

''But some of the Weed Whacker and chainsaw engines are less than 1 cc. This is 850 ccs. You can't hear yourself think when you're around it. But it's not too bad when you're inside with one of the new [full-face] racing helmets on.''

The good news for Christ's neighbors is that he does not turn the ignition too often in Breinigsville. The little orange No. 25 is the 1960 Saab 93F he enters in vintage sports car races and hill-climb events.

Christ's latest plan is to run the Saab in vintage sports car races that are on the undercard for the coming weekend's 12 Hours of Sebring. Christ left earlier this week for Florida, towing the race car on a trailer behind the 1979 Chevy Van that serves as road headquarters for his Vintage Saab Racing Group.

''There's not a lot there to look at, compared to a modern car,'' Christ said after popping the Saab's hood last week. ''Spark plugs, wires, an air cleaner, a one-valve carburetor, a fan, a fan belt and the engine.

''This originally came with a 750 cc motor, but this is an 850 cc motor of a later production model. But it is a three-cylinder, two-stroke Saab engine — no valves, no oil pan; the oil goes in the gas.''

Despite the availability today of synthetic oil, the two-stroke motor still produces more than noise pollution.

''We call it the Bug Killer' because it puts out a smoke screen,'' said Peter Dunn, a Chatham, N.J., racing enthusiast who is one of Christ's competitors and friends. ''I guess it's a little less of a smoke screen [than before synthetic oil], but you can see it.''

Don't be fooled by those descriptions or the orange No. 25's almost cartoonish appearance. It can be pushed to 105 mph in straightaways. That's a speed that is nowhere near the fastest in vintage racing, but it keeps the car in action.

''Vintage racing is a gentlemen's sport,'' Christ said. ''You are out there going as fast as you can go. It is not a half-speed event. But there is no pushing and bumping in corners. There is no taking wild chances where you might have an accident.''

The 44-year-old recalled an instance at Watkins Glen, N.Y., last year in which he had a chance to pass the lead car in a corner. ''But the other car might have hit me, or I might have put him position where he would have lost control,'' Christ said. ''I [backed off] and lost second place and took third. Aggression is not tolerated in vintage racing.''

So Christ's Vintage Saab Racing Group, which also will run a second car driven primarily by Randy Cook of Watkins Glen, will not be at Sebring with visions of doing whatever it takes to win Thursday's one-hour vintage car endurance race or Friday's 30-minute sprint. The Saab Racing Group cars also will appear in practice runs and, prior to Sebring's main event, parade laps.

''If I were driving a faster, more competitive car, it might be, We're going to win,''' Christ said. ''For me to say that sounds real good; it sounds real macho, race-car cool. But we're going to participate and be part of the show.''

Christ has many reasons for speaking passionately of the vintage racing scene. His father, Joseph Christ, is a retired Bethlehem School District teacher who spent much of his spare time racing all sorts of vehicles in the 1940s-60s. Joseph Christ's last race car was a 1959 Saab that also was painted Omaha Orange and adorned with white circles and black No. 25s.

The 1960 Saab 93F Charles Christ drives has a body that was originally part of a car that wrecked during a Weatherly hill climb. That body sits on a chassis that was built years ago by Joseph Christ. The car was purchased by Charles Christ last year and has replaced the Austin Healy he used to drive in vintage car races.

But Charles Christ is not a rich suburbanite with money to burn. He puts his associate's degree in automotive technology to work as a self-employed restorer and rebuilder of vintage sports cars. And he is quick to note he lives in ''a modest, two-bedroom home'' with his wife and young son.

The Saab 93F cost him $2,300. He drives it while wearing a fire-resistant racing suit and accessories totaling roughly $1,000. Some of the costs, including the $300-$500 entry fees required for each of the dozen or so events he enters each year, are defrayed by sponsors, most notably Saab Cars of North America.

As with nearly anyone else who is devoted to a hobby, however, Christ often reaches into his own wallet.

''I don't have a large bank account or millions of dollars,'' Christ said. ''But [in another sense] I am a millionaire. I have my wife and [6-year-old] son. I have a place to live, and I have my play toys. … I really feel sorry for the people who are out there going to work every day saying, My life sucks. I hate my darn job. I hate my darn commute. I hate my darn boss. I can't wait until 5.' They spend their whole life up to retirement doing something they never enjoy.''

No animosity

Many of the drivers Christ competes against make six-figure annual salaries in professions such as lawyers, doctors and stock brokers. They drive such upscale cars as Camaros, Mustangs, Corvettes and Ferraris in the same events in which Christ says his orange Saab is ''the slug on the track.''

Other race teams also arrive at events with SUVs or bigger vehicles pulling trailers that would make some NASCAR teams envious.

''There's no animosity,'' Christ said. ''I don't pull up in my van and they go, Here comes that *%$*&@# with no money.' Maybe someone thinks that, but it is not evident. I can walk over to anyone of those gentlemen and say, I have a spark plug problem,' or, I need something welded. Can you help me?' And they will. Vintage racing is like that. In vintage racing, it is in the spirit of the event.''

Dunn, Christ's friend, who works in Manhattan in the insurance industry, admires what Christ has done with ''a budget car.'' And he said Christ has something in common with all the other racing enthusiasts.

''You have to be out of your mind to get involved with this,'' Dunn said. ''You have to be a little crazy.''

In the least, Christ is one of vintage racing's more spirited participants.