I found this in the Powertrain guides...

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Northstar 4.6L V8 4565 cc / 279 ci DOHC 4 valves/cyl 275 HP @ 5600 RPM 290 lb-ft @ 4400 RPM Buick Lucerne LD8

Northstar 4.6L V8 4565 cc / 279 ci DOHC 4 valves/cyl 275 HP @ 5200 RPM 292 lb-ft @ 4400 RPM Cadillac DTS LD8

Northstar 4.6L V8 4565 cc / 279 ci DOHC 4 valves/cyl 291 HP @ 6000 RPM 286 lb-ft @ 4400 RPM Cadillac DTS L37

Northstar 4.6L V8 4565 cc / 279 ci DOHC 4 valves/cyl 320 HP @ 6400 RPM 315 lb-ft @ 4400 RPM Cadillac SRX, Cadillac STS LH2

Northstar 4.6L V8 4565 cc / 279 ci DOHC 4 valves/cyl 320 HP @ 6400 RPM 310 lb-ft @ 4400 RPM Cadillac XLR LH2

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So what creates the difference in these motors that it makes 275HP and 291lb-ft of torque in the Lucerne/DTS, but up to 320HP and 315lb-ft of torque in the SRX/STS? I am guessing different cams, valves, size of ports???

Edited December 19, 200618 yr by CreativeVision

The DTS and Buick both use the Non-VVT engine...

...not only that if GM chooses engine output can be controlled considerably by ECU tuning.

What I don't understand is why they wouldn't put the 291hp Northstar as standard in the DTS... and standard in the Lucerne CXS... after all, it is supposed to be the "sporty" Lucerne... the more power, the better, no? I understand you have to mash the gas a little harder to get it, but again, it's the "sporty" Lucerne.