ROMEO, MI – There’s a mini-trend in the auto industry the Green Party, the Sierra Club and the National Highway Traffic Safety Admin. probably hope you’re not a part of: the exploding market for low-volume, specially made high-performance variants of cars, trucks and even SUVs.

In fact, although the relative volumes remain miniscule enough to fly below the environmental and safety lobbies’ radar, almost every volume manufacturer is cranking up efforts to entice the extremely discriminating buyers of these pricey and usually quite exclusive models.

Checking components prior to installation in hand-built engines on Ford niche engine line.

These typically well-heeled customers aren’t those over-exposed “tuner” types hanging gargantuan spoilers and sewer-pipe exhausts onto their otherwise mundane rides – they want to buy their rockets straight from the factory.

In addition to the long-established innovators – BMW AG’s M division and Mercedes-Benz’s AMG – General Motors Corp.’s Cadillac division is expected to expand its V-series high-performance lineup and Chrysler Group has its fledgling SRT, or Street and Racing Technology (formerly Performance Vehicle Operations). Honda Motor Co. Ltd.’s Acura and Honda Type S models are strong sellers and most of the other Japanese manufacturers, normally more circumspect, are joining in, too. (See related story: Dodge Changes Performance Unit Name)

Ford Motor Co.’s Special Vehicle Team, meanwhile, has been in the business for more than a decade, longer than any competitor apart from BMW and Mercedes. With this experience – although SVT models currently are out of production until new models arrive for ’06 – Ford reckons it knows the customers for “factory tuned” special models pretty well.

That’s why Ford has kept alive its “niche” engine-building assembly line here, in a 22,000 sq.-ft. (2,044 sq.-m) outbuilding of the vast plant that assembles 4.6L and 5.4L modular V-8s at a pace of about 800,000 a year.

Ford and rival General Motors Corp. both have chosen to emphasize the engine-building part of their specialty-vehicle operations. GM announced late last year that it, too, will build low-volume, high-performance engines in a special facility near Detroit.

Ford’s niche-engine assembly line will make about 1,200 engines this year – an amount equal to about a half-day’s production from the bigfoot plant next door.

But that is the kind of production volume that resonates with the acronym customers who buy SVT, SRT, AMG. The lower the better – low volume means exclusivity. Special attention not lavished on “regular” cars and the engines that power them.

Right now, it doesn’t get much more exclusive or “special attention” than Ford’s niche engine line: Before, the niche-assembly process built the supercharged 4.6L DOHC V-8 for Ford’s Mustang Cobra SVT, but with the Cobra on hold until an SVT variant of the all-new ’05 Mustang is engineered, the niche-engine assembly team – just nine technicians in all – is building engines exclusively for that most-exclusive of Ford products, the all-new, $140,000 GT supercar.

For the GT’s thundering supercharged 5.4L DOHC V-8, two-man teams build each engine, walking with it as it progresses through a dozen workstations that take it from a bare block and cylinder heads to a finished supercar engine that churns out 550 hp. It happens at the rate of around nine engines each day.

Each GT engine takes about 2.5 hours to build, says Mike Eller, team manager on the niche engine line. When the engine is finished, a plate is bolted on, stamped with the names of the two technicians who built it. This detail is the icing on the cake for this kind of customer, underscoring the elite status of their purchase.

Although it all sounds like the ultimate marketing scheme, the niche-assembly strategy does deliver on the promise. Ford executives say no engine made on this line – Cobra engines have been built here since 1996 – ever has been returned for a warranty problem that can be traced to improper assembly. The hand-built engines assembled here simply don’t break.

Eller tells Ward’s the long-revered engine-assembly process known as “balancing and blueprinting,” where individual components such as pistons, connecting rods and crankshaft bearings are hand-selected and matched to ensure high-quality tolerances, comes automatically for each and every engine crafted on Ford’s niche-engine line.

First, he says, quality-control measures are so stringent for suppliers of components such as pistons and connecting rods, those parts essentially come to the niche line with the sort of extremely close tolerances that old-fashioned balance-and-blueprint methods couldn’t replicate on their best day.

Many engine parts, with their known dimensions, are sorted and cataloged by a computer system that mates specific “batches” of crankshaft bearings, for instance, with a batch of connecting rods with dimensions that best match the bearings. The system automatically guarantees the ideal matching of specific components.

The niche-engine teams already are experts about every detail of the titanic GT engine. Those hypnotically blue valve covers, for instance, are not that shade of blue by mistake. The color specially was chosen by Camilo Pardo, chief designer for the GT.

“It’s not standard Ford blue-oval blue,” says a technician. “It’s a different shade. At first we had to get used to it, but now it looks perfect for this engine.”

You won’t get that sort of trivia on the 2,500-engines-a-day line next door.