: 1999 Northstar engine 85K Miles, How can one tell if is good

04-25-06, 07:59 AM
Found this for sale with the trans for $1000, sitting on a garage floor.
Sold as is, they are still parting out the car.

The lower cover of the engine is cracked, the shop said they broke it
dropping the front end and it hit the concrete.

1999 Northstar engine 85K Miles
Its from a wreck, assume an insurance auction.

How can I determine if the heads are good ?
1) Cylinder leak down test ?
2) Milk shake in the pan

Will any 1999 from a two door fit my DeVille Ele' ?

Thank You

04-25-06, 11:58 AM
Yes, to check the head gaskets, do a cylinder pressure test and watch for bubbles in the surge tank.

What car did this engine come out of? I think you have a 275 hp engine. You can't use a 300 hp engine (STS, DTS or ETC)

04-25-06, 12:12 PM
Please explain why the different engines cannot be exchanged if they are both 4.6 liter engines from 1999. I am new to NorthStars.

Are there physical differences or computer controls or transmissions differences that could affect a swap ?

04-25-06, 01:01 PM
The cams on the engines are different. I think there's one other difference, but your computer is specially programmed for the 275 HP Northstar, so if you try to dump the 300 HP engine into it, it won't run very well, or maybe not at all.

04-25-06, 02:17 PM
Yes, the two different engines (vin9 vs vinY) use different intake cams, PCMs and final drive ratios.

04-25-06, 02:30 PM
So the ECM (computer) would run the external systems (fuel...) incorrectly for the cam in the engine.

If that was the case, with two engines sitting side by side could the cams be exchanged from the 275hp to the 300hp engine.

If yes, can the cam exchange be performed without pulling the heads on either engine ?

This is a learning experience for me.

04-25-06, 02:36 PM
I assume "final drive ratios" is for the transmission, 1-4th gear and OD based on the transmission model and engine HP ratings.

So if the engine could be used, the transmission could not.

04-25-06, 06:09 PM
Just checked, the 1999 4.6 Northstar is from a 2 Dr Eldorado.

If is is a "9" and not a "Y" can the long blocks less the cams be exchanged ?

Is there a code on the block to determine if the engine is a "Y" or "9" ?

04-25-06, 07:54 PM
Cams can be changed, but I am not sure if there are any sensors that are different. Don't think so, but I am not positive. I don't think the heads need to be removed to get the cams off. I am sure there is an identifying number or marking somewhere on the engine but someone more knowledgable will have to help there. Yes, final drive ratio is refering to the transmission and the two should not be swapped to different engines.

05-04-06, 08:44 PM
Just ran the leak down test on my northstar, nothing when tested between 100 and 125 psi.

Is this a good test, especially when looking at an engine that some one pulled to be used as a replacement ?

What other test can be performed on an emgine out of the car ?

05-04-06, 09:03 PM
That test is 100% positive. If there where no bubbles in the cooling system, the head gaskets are good.

05-05-06, 07:04 PM
head gaskets can fail between 2 cylinders