The industry’s population of inline 6-cyl. engines is dwindling, their chief environment – rear-wheel-drive platforms with yards of hood length to accommodate their typical north/south orientation – disappearing at a rate akin to that of tropical rain forests.

The one application for which the I-6 layout – renowned for its smoothness and perfect internal balance – seems perfect: light trucks. Yet the number of inline 6-cyl. engines in a true light-truck application numbers just one: General Motors Corp.’s Vortec 4.2L I-6.

Almost the entire automotive world has defected to the V-6 layout, largely due to packaging flexibility, need for more frontal-area crush space to comply with tougher safety regulations and a trend toward vee-engine modularity.

GM engineers knew when they introduced the Vortec 4200 four years ago they were bucking the trend. Even more chilling, the design had to be approved slightly more than three years prior to launch. Yet GM’s faith in the intrinsic goodness of a well-engineered I-6 prevailed, and the Vortec 4200 comes to the ’05 model year as strong as ever, winning a fourth consecutive 10 Best Engines award.

GM’s Vortec 4200 I-6 represents a genuine engineering and manufacturing achievement.

Time and again, the Vortec 4200 surprises Ward’s editors with its continuing crispness and “just right” balance of power and refinement. Four years into their lifecycles, many engines feel aged and maybe even out-of-sync with the market. Some are freshened with extra power, extra torque, perhaps more displacement.

The testimony to the wisdom of the Vortec 4200’s initial development goals is the fact that since ’03, when power was bumped slightly from 270 hp to 275 hp, the Vortec has required nothing, save minor component refinements, to stay fully competitive.

The Vortec 4200 is unquestionably the most refreshing, entertaining and powerful “base” engine in the light-truck market. Its refinement befits a luxury car, its brawny side unveiled only when you need to use it like a truck’s meant to be used. At just 1,800 rpm, 90% of the Vortec 4200’s torque is at attention, tugging better than any V-6 we’ve tried.

For ’05, slight internal modifications improve the action of its variable valve timing system (which acts on both the intake and exhaust cam), enhance throttle response (never a problem with this engine) and reduce radiated noise. But the Vortec’s basic technology package – all-aluminum construction, infinitely variable valve timing, electronically controlled throttle and direct-mount accessories – still is highly competitive.

Our only criticism of the Vortec 4200 rests with GM’s inability to find another home for it in addition to the company’s multi-model midsize-SUV lineup. Almost since the beginning, Ward’s 10 Best Engines testers have said this engine would be a delight in any number of entry premium or luxury sport cars.

The Vortec 4200 remains a special treat, a genuine engineering and manufacturing achievement. GM, here’s our future-application advice, free of charge: Saturn Sky and Pontiac Solstice roadsters.

General Motors
Vortec 4.2L DOHC I-6
Engine type 4.2L DOHC I-6
Displacement (cc) 4,160
Block/head material aluminum/aluminum
Bore x stroke (mm) 93 x 102
Horsepower (SAE net) 275 @ 6,000 rpm
Torque 275 lb.-ft. (373 Nm) @ 3,600 rpm
Specific output 65 hp/L
Compression ratio 10:1
Application tested Chevrolet TrailBlazer
Fuel economy for tested vehicle (EPA city/highway mpg) 15/21

bvisnic@primediabusiness.com