: 2001 Northstar 4.6 in 99 sts body??

09-08-07, 10:04 PM
Hey guys, I came across an engine today to replace the cracked block in my car. The only problem is that it came out of a 2001 sts, and my car is a 99. What is involved in converting it to work? It looks to be very close, however there is an air pump and lines and the coils are inside of the valve covers instead of the back. Can i use the old distributer/coils and what not, so that all wiring is the same or are there differences? Has anyone successfully done this job?

09-09-07, 09:55 PM
Hmmm...nobodies done this? Basically this guy has the whole assembly-transmission, subframe, motor, electrical etc. I was thinking I could change over the electrical components from the old motor onto the new one, and also use the old exaust manifolds to get rid of the air pump. It looks very similar, would cadillac have changed it enough that they are non transferable?

09-09-07, 10:36 PM
This question is a little different than the other one you posted.

Even with the whole subframe assembly I don't know if the harness would swap pver. You would have to use the computer that matches the engine.

Again, it's probably easier to get the right block.

09-10-07, 06:15 AM
As stated in the other thread, too many differences... I forgot about the ignition system, they are totally different.
Go find the right engine.

09-10-07, 06:34 AM
This is an info about the differences and hope it is suitable for you :)

The list of new Northstar V8 features includes:


Roller-follower valvetrain design

Improved combustion chamber configuration

Center-feed intake manifold

New pistons

Coil-on-plug cassette ignition system

Siemens powertrain control module (engine/transmission control computer)

Exhaust manifolds with integral air-injection passages

Flex pipe between the exhaust Y-pipe and the catalytic converter

Twin electrically driven, two-stage air pumps (LEV applications only)

Direct mounting of all engine-driven accessories (power steering pump, AC compressor, electrical generator)

Integrated coolant crossover and throttle-body support

The Northstar’s fuel recommendation changes from premium (93 octane, lead-free) to regular, resulting in a major reduction in operating expense. To facilitate this gain, the Northstar’s compression ratio was lowered from 10.3:1 to 10.0:1.

One result of these improvements is that the 2000 Seville will be certified for sale in California and certain Northeast states as a low emissions vehicle (LEV). This was achieved by means of a reaction-heated catalyst, pistons with reduced crevice volume and a new combustion chamber design.

Engine Design Changes
Revised combustion chambers are superior to previous designs in terms of both tumble motion of the incoming fuel-air mixture and burn rate. The intake and exhaust valves have been resized. Larger intake valves improve the engine’s breathing ability, while smaller exhaust valves increase flow velocity, an aid to catalyst light off.

While the new combustion chamber design helps maximize fuel efficiency, even larger gains are made by the addition of roller-follower devices between each cam lobe and valve stem. Compared to the previous Northstar’s direct valve actuation, the result is a substantial reduction in friction. During moderate driving conditions, the torque necessary to turn Northstar’s four camshafts is reduced by 50 percent or more.

The Northstar also benefits from a new ignition system that delivers power to the spark plugs directly instead of through wiring. A cassette containing four ignition coils linked by short secondary leads to adjoining spark plugs now attaches atop each cylinder head cover.

In addition to improved reliability, the new ignition system permits scheduling the magnitude of the voltage sent to the spark plugs. High voltage is used during full-load, high rpm and heavy EGR (exhaust gas recirculation) conditions to guarantee complete combustion. The energy level is reduced to minimize electrical loads and radio frequency interference during light-load conditions, such as medium speed cruising. The result is extended spark-plug life and a peak energy capacity that is 130 percent higher than the system it replaced.

Northstar’s new powertrain control module is a single circuit board device housed within a sealed aluminum case engineered to withstand the harsh underhood environment. The module contains dual microprocessors to monitor and direct engine and transmission operations.

Noise and vibration improvements are the result of adopting a center-feed design for the composite-plastic intake manifold, as opposed to the previous end-feed design. The new design facilitates a near equal-length induction path for all eight cylinders. In contrast, the previous design provided a long path to the front cylinders and shorter paths to rearward cylinders. With the reduction or elimination of many harmonic tones, the resulting induction sound is more of a hum.

A molded-plastic cover backed with acoustical foam rests above the intake manifold to reduce induction, fuel-injector and other noises radiated by the engine. Direct mounting of accessories eliminates flex and vibration inherent with extra brackets. A flexible connection in the exhaust system en route to the catalyst helps quell another source of noise and harshness.