uto enthusiasts often say the engine is the heart of a car, especially in exotic nameplates like Ferrari or Lamborghini. In those cars, the engine gives a car its "personality." The engine, though, is important in any vehicle. Maybe not as a defining element of the design, but clearly as the power source. Without an operating engine, the car is dead. And like the human heart, engines wear out. When that happens, owners have a major financial decision: Put money into the car, or get a different one.

Engine repair "Repairing an engine can get expensive," advises Dave Van Sickle, AAA's director of automotive and consumer information, reaching as much as $5,000 for a complete overhaul of your common American, small, V-8 engine. If you know specifically what's wrong, like a valve job, the expense can be much less.       With a partial overhaul, though, you have an engine that's just half "new." Keeping it for a few more years, you could face another partial overhaul on the rest of the engine. And when you overhaul part or all of your own vehicle's engine, you do know the engine's history.       So why not just replace the entire engine? The decision on a four-year-old car is different than for one eight years old. If you drive a lot of miles commuting, say 120 miles a day (yes, there are people who do!), the warranty has expired not because of time, but miles. A four-year-old car with 120,000 miles should have a lot of life in it. The cosmetics--body, upholstery, trim--usually still are in good shape.       Mechanical parts, though, are part of the equation. Putting money into a replacement engine doesn't get you a new car. The transmission still has the odometer's miles on it. If you fix the engine, will the transmission need fixing six months later? A rejuvenated engine can hasten the failure of other aged drivetrain parts.

With a partial overhaul,       you have an engine       that's half new.

Recycled engines Recycled engines are something different. These are not engines out of derelict vehicles, worn out and abandoned. These are engines from insurance companies' total losses, some with surprisingly low mileage. Another key point--you get all the support parts!       Mileage plays a big factor in the price of these engines. A recycled Ford 5-liter V-8 costs about $900 with 30,000 miles on it, but only $400 with 80,000 miles. Those prices are typical at Lacy Auto Parts in Richmond, Va. "A good used engine for a mainstream vehicle should be $1,000 or less," according to Ed Lacy.       Supply and demand affect price, too. Art Heberer, at Import Auto Recycling, Salem, Va., has seven Honda Civic engines in stock for $400 to $550. "They just don't break. Everybody has them."       Upscale, high-tech engines up the ante. A good, used Mercedes-Benz 4.2-liter V-8 can be $2,200 to $3,000, Heberer says. With computer networks linking recyclers, it's easy for specialists to learn the supply situation elsewhere.       Warranties are variable on recycled engines, even at the same recycler. Heberer's standard is 90 days, but he would consider a year on some Hondas, for example, again citing their "don't break" reputation.       At Lacy Auto Parts, the base warranty is 100 days, but buying a one-year extended warranty can add about 10% to the cost. Buyers need to know if the warranty covers installation labor. Historically, it hasn't, but Ed Lacy says, "That's changing."       Not every repair shop installs recycled engines. Some recyclers can swap engines themselves, others can direct you to a shop that can do it. Figure on $350 to $600 for installation, Lacy adds.