Customers who chip in the substantial extra cost for vehicles crafted by the various auto makers' in-house tuners want, first and foremost, enhanced performance. But they're also chasing something more elusive in this day of $30,000 Benzes and McMansions in every suburb: exclusivity.

And for the horsepower-hungry, what can be more exclusive than a thundering powerplant lovingly assembled by hand just for you?

That's the customer-machine connection the performance-tuning divisions seek to inspire with engine-building operations that say “artisans at work” rather than “robots on duty.”

Mercedes-Benz's AMG started it all, in a philosophy they've coined “One Man, One Engine.” At AMG's engine-building HQ in Affalterbach, Germany, a workforce of 45 master builders is responsible for constructing the big-power engines for every AMG-modified vehicle.

Each man in the shop builds just two or three engines daily, and none are made to feel hurried. If that all-aluminum supercharged V-8 isn't ready today, that's OK — tomorrow will do.

When the engine is completed, the assembler affixes a metal tag bearing his name. The ultimate symbol of pride — and accountability — when just across the dale, Mercedes assembly lines are churning out thousands of engines in the time it takes AMG to construct around a hundred.

Newest to the hand-built credo is General Motors Corp.'s Powertrain Div. Later this year, its immaculate new Performance Build Center in the Detroit suburb of Wixom will quietly ramp up — not a clanking conveyer or transfer line in sight here — for its own spin on the exclusivity guarantee.

GM's $10 million investment in the Performance Build Center is similar to AMG. Fifty to 60 highly experienced engine builders each will construct, by hand, the imposing 500-hp 7L V-8 for the soon-to-be-launched, Ferrari-fighting Chevrolet Corvette Z06 and the supercharged 4.4L DOHC V-8 for Cadillac's V-Series performance vehicles, the STS-V and XLR-V.

The vehicles all are engineered by the GM Performance Div., but it's no accident the Performance Build Center's hand-built engine program is a focal point — GM Powertrain engineers went on-site to study AMG and other specialty engine building operations all over the world.

“It's about pride of ownership,” says Timothy M. Schag, the Performance Build Center site manager who's held manufacturing posts throughout the GM universe. “You can open up the hood, show someone the engine is hand-built.” Whether in the U.S. or Germany, the performance divisions know the engine should be the star of any tuning operation.

Inside the 100,000 sq.-ft. (9,290 sq.-m) Performance Build Center, each builder selects an engine block and other major parts from the on-site component corral, then dollies the engine through 15 stations that ultimately produce a ready-to-run high-performance engine.

Schag says there hasn't been a final decision on whether each engine will wear an AMG-style plate bearing the assembler's name, but he's “90% positive” it will happen.

“There's also uniqueness in terms of numbers,” he adds. While the GM empire knocks out tens of thousands of engines daily, the Performance Build Center's annual output currently is pegged at 15,000 — or about one engine every four hours for each builder.

Schag says the low numbers and lack of high-volume assembly processes won't mean any compromise of reliability, either. He stresses one of the overriding precepts behind the Center's hand-built engine philosophy is to use the same high-volume quality processes that have made GM's recent Global Manufacturing System (GMS) so successful. That includes, Schag predicts, TS 16949 certification (the new international standard for manufacturing-process quality) later this year.

At Ford Motor Co., there's a variation on the theme. The process at Ford's “niche” engine-assembly line on the site of its giant Romeo, MI, engine plant, is “Two Men, One Engine.”

With products from Ford's Special Vehicle Team suspended until a new SVT Shelby Cobra GT500 variant of the '05 Mustang is launched, 2-man teams on the niche engine line — only nine technicians in all — assemble just one engine: the supercharged 5.4L DOHC V-8 for the GT supercar.

The 22,000 sq.-ft. (2,044 sq.-m) niche line also built, starting in 1996, the supercharged 4.6L DOHC V-8 for the Mustang Cobra SVT until the car's temporary discontinuation last year. With the GT's V-8 currently its only output, this specialized operation assembles about 1,200 engines annually.

Each GT engine takes about 2.5 hours to build up from bare block and heads, Mike Eller, team manager on the niche engine line, told Ward's last year.

The 2-technician teams push each V-8 through a series of 12 stations, and when it's finished, you guessed it — a shiny aluminum plate inscribed with the name of both engine builders is affixed to the engine.

Ford recently installed a similar operation for its Aston Martin Lagonda Ltd. unit. At the Aston Martin Engine Plant, on the site of Ford's high-volume Cologne, Germany, engine assembly facility, one technician will build an Aston V-8 or V-12 from bottom to top. Ford figures on 5,000 hand-built engines annually from AMEP.

Although the loving treatment and artisan talent lavished on these hand-assembled engines is meant to verify the elite status of a performance-division vehicle, if Ford's experience is any indicator, there's at least one decidedly tangible benefit: Ford says no engine built on its niche-assembly line ever has had a warranty problem attributed to improper assembly.