THE THING ABOUT THE NORTHSTAR ENGINE
It is a wonderfull powerfull powerplant which fits Esprit engine bay.
It was originally conceived as a high-performance engine to compete against German-made luxury sports cars. It had evolved from the Corvette LT5 all-aluminum V-8 designed
for Chevrolet by Lotus
. It has since become the V-8 powerplant of choice for General Motors.
A supercharged 4.4-liter version was developed exclusively for the 2006 to 2008 Cadillac XLR-V and STS-V models. The supercharged XLR-V generates 443 horsepower while the STS-V version produced 469 horsepower.
Read more: Cadillac Northstar Engine Basics | eHow
It could be easily hopped up to 600-700HP (ZF box needed)
Anyone considering conversion, please read this:
Worth it for Aurora 4.0 Northstar / 4T80E?
GM didn't fix the NorthStar block(that goes for ALL of them 3.5,4.0,4.6) until 2004. The early NorthStars 92.5-1999 used a short fine pitched head bolt (same bolt as the Quad4) and almost all of these engine will have the headbolts pull out of the block (just like a Quad4) and will need a VERY expensive head bolt project completed... On these cars the car is removed from the engine... Failed head gasket fix at the dealer with proper replacement head bolt studs or timeserts will cost $5000 and up.
Then, in 2000 (after only 8 years !) GM realized that they had a problem and replaced the short fine pitch head bolts with longer fine pitched head bolts. These engines (3.5,4.0 and 4.6) are considerably better then the early design... but are by NO MEANS bullet proof... There are still LOTS of reported head bolt failures and half case leaks in these years too. Again... cost to fix $5000 and up.
In 2004 (of course the Aurora was already dead at that point), GM realized that they STILL had a problem and replaced the long fine pitched bolts with long coarse pitched bolts (very much like the bolts on the LSx engines) and the problem is MUCH less now.. though there have been reports of failed head bolts on 2004-current NorthStarts too.
You'd be better driving the donor car (if driveable) before buying the engine. You need to do some homework...
1) Drive the car until it gets to operating temperature, preferably up and down some steep hills... with the A/C on... Watch the temp gauge... if the needle moves off of straight up RUN from the car
2) Buy a exhaust/coolant test kit from Pepboys (or where have you) and test the antifreeze for exhaust gases.. (any quality mechanic can do this for you) If there is any evidence of blow by in the coolant RUN from the car
3) Ask to see all of the service records for the car... look specifically for coolant servicing. You want to see the coolant being serviced every other year.. at a minimum... If the car has gone 5 years between coolant changes...or if the first and only one was just done.. RUN from the car.
4) Have a mechanic run a compression check and leak-down check on the motor (they should do that for you for less then $200). If any cylinder is widely different from the others... Well you know the drill
5) Lastly the Transmission on these cars has its quirks too. Look for a tranny leak out of the driver's side output shaft... any leak here means that the support bearing for the output shaft has shattered (a very common problem) and the transmission is on its last legs. ... you know Run.
Oh one last thing... if the car has an intermittent stall on warm up. That is also very common on 2000-2003 cars. That is the Crank Sensors... Those are easy and cheap to replace.