General Motors Corp.'s Cadillac division unveils a wholesale reworking of its signature engine, the Northstar, as engineers prepare the V-8 to power two all-new models.

The Northstar V-8 retains its 4.6L displacement, 90-degree layout and DOHC architecture but is heavily revised to fit longitudinally and drive the rear wheels — or all wheels — in two '04 Cadillacs, the XLR roadster and SRX cross/utility vehicle.

Northstar's use in the two models will mark the first time since its 1992 launch that the V-8 is fitted in a vehicle that is not front-wheel drive.

For the SRX and XLR, the new Northstar develops 315 hp at 6,400 rpm and 310 lb.-ft. (420 Nm) of torque at 4,400 rpm. The current Northstar produces up to 300 hp and 295 lb.-ft. (400 Nm) of torque.

John Zinser, GM Powertrain chief engineer for Premium V engines, says 80% of the Northstar is new.

Aside from the power-enhancing improvements — achieved largely through the use of an infinitely variable valve-timing (VVT) system for intake and exhaust valves — Zinser says emphasis was placed on the new Northstar's sound quality.

Engineers want to place the new Northstar squarely between the ultra-hushed Lexus V-8 and the often-vocal BMW V-8. The electronically controlled, hydraulically activated VVT system is a first for the Northstar, as is its new electronically controlled throttle.

GM says it has invested heavily to install new tooling and machining at the Northstar's assembly site in Livonia, MI. There are all-new engine-assembly and cylinder-head subassembly lines, improved machining capability and upgrades of error-proofing and cold-test processes.