Will a 1999 northstar cadillac engine fit in place of 1997 north star engine?

While both are Northstar engines, a direct swap isn't guaranteed. There are subtle differences between Northstar engines produced across different years, even within the same model Cadillac. You need to check the specific engine codes (found on a tag on the engine block) for both the 1997 and 1999 engines. Even if the engine codes are very similar, there could be differences in:

* Mounts: Engine mounts may have slightly different positions or bolt patterns.

* Wiring harness: The connectors and harness may not be fully compatible. You might need to do some wiring splicing or adaptation.

* Sensors: Sensor locations and types might vary.

* Exhaust System: The exhaust manifolds and routing could differ slightly.

* Accessories: Power steering pump, alternator, etc., might have different mounting points.

In short: It's *possible* but not *certain*. You'll need to compare the specific engine codes and physically compare the engines before attempting the swap to determine if it's a feasible, straightforward installation, or if significant modifications will be required. Consulting a Cadillac repair manual for both years is highly recommended.