Detuned Cadillac Northstar V8 Engine

[GXP]

First of all, I'm not a gear head. Novice at best, so here's the question.

Looking at getting the most out of my 4.6-liter Northstar V8. It's the same aluminum power plant you find in Cadillacs, only detuned to produce 275 horsepower and 300 lb-ft of torque. Which is about 25 less than the Cadillac. I know there's got to be someone lurking in here that knows the answers. I feel more at ease getting the info first here than at a pro shop or dealer...

Thanks

Jeff

[GXP]

Alrighty Then........

I will certainly give that a try

[jamz]

I'm not to familar with that engine so I don't have much to say .. anyone have any thoughts for him?

[GXP]

Originally Posted by jamz

I'm not to familar with that engine so I don't have much to say .. anyone have any thoughts for him?

From one nerd to another, I appreciate your efforts. I'm at least smart enough to know that not every question can be answered. I was just kind of hoping somebody had already made this upgrade and could tell me if it was worth it or not.

Keep up the good work and Thanks

[darkfox]

in situations like these, gm typically makes the following changes to "detune" the engine:

different PCM software
different intake and exhaust manifolds
different exhaust system
different intake system

also they may be under-rating the engine.

you may look into the manifolds and intake/exhaust systems first to spot any differences as opposed to the caddy versions.

also, the 2005+ grand prix GXP has 303 horsepower with the same engine, which is interesting... you may look at swapping the PCM or getting a reflash using a vin from one of these vehicles. it may be a direct swap.

but i am just guessing since i also have little experience with these engines. hope i have been of help.

[jeremy96gase]

First off GXP welcome to the Forum!
I don't know too much about Caddy engines, but here's the info I know.

There where several years the 275 HP rating was attached to Cadillac Vehicles. For instance the Seville SLS (275) vs STS (300).
Also the DeVille DHS (275) vs DTS (300).

As Darkfox said, intake and exhaust systems are likely the change. The Block/Heads/internals are probably the same between the two.

Originally Posted by darkfox

also, the 2005+ grand prix GXP has 303 horsepower with the same engine, which is interesting...

The 05+ Grand Prix V8 uses a Small Block 5.3L. The same small block found in the 06+ V8 Impala and 06+ V8 Monte Carlo.

[GXP Mike]

If I remember my articles right, the detuned nothstar in the Bonnie is a destroked version of the 4.6. I think it's something like 4.4L. Have you googled or gone on e-bay to see if any one makes parts for your car?? When in doubt, join a Bonneville club like West Coast Bonnevilles.
As for the GP GXP, it is a 5.3L LS-4, or baby Corvette motor, not the Northstar engine.

[jeremy96gase]

Originally Posted by GXP Mike

If I remember my articles right, the detuned nothstar in the Bonnie is a destroked version of the 4.6. I think it's something like 4.4L.

The GXP Promo car had a 4.4L Northstar, but all Production Bonneville GXP's had the 4.6L 275HP engine.

[gmforlife]

Yah, GM takes a lot of the same powerplants and then proceeds to "detune it" for different vehicle applications. For instance, the duramax diesel in the Express Van is the same motor as in the silverado HD's, but like 50 hp difference. Also, in the Express Van the motor is backed up by a 4l80E transmission and not the beefy Allison. So Gm usually has their reasons on different vehicle applications.