: Rebuilding a Northstar engine



BeelzeBob
01-31-03, 07:58 PM
So.. What does it take to rebuild one of these things? One of the things I used to worry about on my ETC was the engine going.. I mean.. Isn't is like $8000.00 to replace the engine? So, are there any rebuild options? What would something like that involve?

elwesso
02-01-03, 04:48 PM
In researching this engine, we discovered that few rebuilders are overhauling Northstar V8s - not because these engines are lasting forever (they're not) but because the Northstar V8s are such expensive and complex engines. Cadillac has no reman program for Northstar V8s (if one fails, replace it with a new one). None of the major production engine rebuilders are doing Northstar V8s, and some rebuilders told us certain critical internal parts are unavailable (such as oversize crankshaft bearings). Add to this the fact that the cylinder liners can't be replaced or overbored and it doesn't leave much to rebuild.

Even the heads are throw-aways, according to Cadillac. If the valve guides are worn, Cadillac says the cylinder heads need to be replaced. The heads have hard powder metal valve guides, but we don't see any reason why the guides can't be replaced with new ones or repaired with bronze or cast iron guide liners.

playaman
02-05-03, 08:39 PM
Ack. That's a bummer. Do you know if the cadillac parts are forged or not? I heard somewhere that the pistons and rods were forged. I've been wanting to up the shot on my nitrous but I'm not sure how much it can take. And, nope, no detonation yet *knock on wood* *crossing fingers*.

elwesso
02-05-03, 08:41 PM
They are forged

playaman
02-05-03, 08:53 PM
Gracias. I just saw that mechtech motorsports (www.mechtech-ms.com) has ran 9psi of boost no prob. Sounds good to me. :)

elwesso
02-05-03, 09:02 PM
9psi doesnt sound too bad. I have heard that any cadillac engine just doesnt hold up well to forced induction. I dont know, i would assume that it could handle it, thats what ive heard.

I personally wouldnt add a supercharger to an engine that didnt come stock with it. Isnt 300hp enough?

playaman
02-05-03, 09:08 PM
I'd like to hit the 650hp range they were hitting, however I don't see that happening anytime soon. I'd like 500 fwhp then I'd be satisfied :) Looks like we're both forum addicts. :)

elwesso
02-06-03, 03:09 PM
TRUE

BeelzeBob
02-06-03, 06:47 PM
A new Northstar engine costs what - $8000.00 plus installation?

elwesso
02-06-03, 08:27 PM
ive heard more than that, more like 10k. Im not sure, you could probably get one for much less from a salvage yard. But i think that cadillac built these engines well enough that rebuilts arent necessary.

Devil_concours
02-06-03, 10:34 PM
they said engine costs 8500 when they replaced the engine in mine. Anyways, I heard that cylinder walls are made out of steel is that true?

elwesso
02-07-03, 04:32 PM
Actually, there cast iron sleeves. They stick them in there, because the aluminum would expand too much.

Brett
02-07-03, 04:59 PM
cadillac has shown a few supercharged applications of the northstar in their concept cars...same northstar to your knowledge or different?

elwesso
02-07-03, 05:09 PM
Well they are contsantly playing around with it, trying to make it smaller but as powerful if not more. not sure if they are the same or not FOSHO.

Concourson20s
05-17-05, 04:24 PM
Well they would have to run a way lower compression ratio for one. No engine with a 10:1 will last long with any kind of pressure added to it. I beleive the sc version had something like 8:1 compression ratio and a tighter oil clearance as well.

As it goes for rebuilding these engines, it's perfectly possible. Don't listen to that quote from that article which was posted above. There is alot of false statements in it. First off northstar heads are only throwaways if they are cracked. Sure why spend the money on parts and labor to replace valve guides? (Which they make replacement ones btw). Any good technician, will throwaway a head with worn guides, if they are looking for a good reliable rebuild. Your better off buying heads with good guides, than messing with the worn tired ones on yours. Whether you have a 305 chevy or a 5.0 mercedes engine. Chances are if the guides in your heads are worn and cracked, the rest of your heads are probably in the same condition. Better off rebuilding a cleaner, lower mileage example. As for the bottom end, true there isn't undersize or oversize "main bearings" available, but you can find rod bearings to all type of specs (the ones that go bad the most). Chances are if you spin a mainbearing the engine just became a good boat anchor anyways. Now true these engine's arn't commonly rebuilt, ofcourse! Parts are expensive as hell, and the price of rebuilding one is almost as much as just buying a long block and putting it in. Thats the only reason they are commonly just replaced. Now if your a tech or a do it yourselfer and you have the knowledge to rebuild one you can do it and save yourself a decent amount of money.

davesdeville
05-17-05, 11:48 PM
Northstar crate engines can be found for around $4000 now.

razeorc
05-18-05, 08:14 AM
Rebuilt N*s are being done by Jasper Engines for around 5k with the headgasket problem fixed along with upgraded valve stems and a few other goodies, oh and it also has a 3year - 75,000 mile warranty, so far it's the best bang for your buck. If you're a DIY, just get one of these and plunk it in, little bit more than a crate even though it's not new but has all of the weaknesses repaired.

ktills45
05-18-05, 12:24 PM
Rebuilt N*s are being done by Jasper Engines for around 5k with the headgasket problem fixed along with upgraded valve stems and a few other goodies, oh and it also has a 3year - 75,000 mile warranty, so far it's the best bang for your buck. If you're a DIY, just get one of these and plunk it in, little bit more than a crate even though it's not new but has all of the weaknesses repaired.

What is the deal with the new headgaskets they use? Anyone care to comment on the durability of those, given the old ones seem pretty sophisticated?

razeorc
05-19-05, 02:43 PM
From what I recall, the origional weren't graphite, but another composite that did not distribute heat as evenly as graphite and thus caused warping, they also contained steel rings. Since the HGs in the 95-98s were insufficently torqued (there's a GM service bulliten regarding the main bolt repair and new torquing procedure that puts more clamping force on the heads) coolant or even moisture from the air could seep in and corrode the steel rings, causing gapping or depending on the location and sevarity of the corrosion, gasket failure.

I am currently looking into possibly replacing my N* if the source of my rough idle on cold start and Hydrocarbons in the coolant are coming from a leaking HG. It could be a number of other things but I will be calling Jasper Engines soon to find out exactly what the difference in the HG is and who manufactures them.

chevyorange
05-20-05, 10:10 AM
Just for giggles, I'm having a 17k Northstar put in my STS as I've had "a problem or two" with the original motor.

Does anyone think that in 17k miles other than putting sand in the oil, could anyone have started this engine on the road to failure by not doing anyting at all?

I'm hoping that with as few miles it has on it that there realy couldn't be any abnormal wear issues starting already. (The car has 190-195 in all cylinders and the leak down was good).

Thanks,

Adam

BeelzeBob
05-21-05, 12:29 AM
From what I recall, the origional weren't graphite, but another composite that did not distribute heat as evenly as graphite and thus caused warping, they also contained steel rings. Since the HGs in the 95-98s were insufficently torqued (there's a GM service bulliten regarding the main bolt repair and new torquing procedure that puts more clamping force on the heads) coolant or even moisture from the air could seep in and corrode the steel rings, causing gapping or depending on the location and sevarity of the corrosion, gasket failure.

I am currently looking into possibly replacing my N* if the source of my rough idle on cold start and Hydrocarbons in the coolant are coming from a leaking HG. It could be a number of other things but I will be calling Jasper Engines soon to find out exactly what the difference in the HG is and who manufactures them.


Northstar headgaskets have always been compacted graphite gaskets...with stainless steel firerings and a stainless steel expanded metal core.

95-98 engines did NOT have "insufficiently torqued" head gaskets. The GM field service bulletine changed the bolt tensioning specs slightly FOR SERVICE. That had no effect on the bolt tensioning done in the engine plant originally when the engine was built. Just the service spec was modified, not the spec used in production.

There is really no difference in the head gasket material, construction, quality or supplier after all these years. Basically, the OEM gasket is the best compacted graphite gasket obtainable. Period.

98 Caddy
05-21-05, 10:34 PM
Bbob, can you tell me what the new torque specs are? Are these applicable to all year Northstars? I checked Helms website and the Service manuals are not for sale for 98 Devilles or 95. Where else can I get Factory manuals? Thanks for all your help and efforts that you put into this site. I for one have learned a lot of useful information from you and others. Keep up the good work! :thumbsup:

BeelzeBob
05-21-05, 11:43 PM
Bbob, can you tell me what the new torque specs are? Are these applicable to all year Northstars? I checked Helms website and the Service manuals are not for sale for 98 Devilles or 95. Where else can I get Factory manuals? Thanks for all your help and efforts that you put into this site. I for one have learned a lot of useful information from you and others. Keep up the good work! :thumbsup:


Tighten the bolts in sequence 30 nm + 60 degrees, then on a second pass give them an additional 60 degrees, then on a final pass an additional 60 degrees. That will work fine. There are several different tensioning specs but they basically do the same thing. With the new gaskets and new bolts and fresh timeserts the 30 nm + 60 + 60 + 60 will be fine.

delzy
05-22-05, 11:24 PM
You can find a factory service manual here:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7975586929&category=34212

razeorc
05-23-05, 01:34 PM
Wow, sorry for the misinfo and thanks for cleaning up my mess Bbob, i'll keep my mouth shut :)

club car
06-04-06, 03:09 PM
i agree i want that hp to i would love to drive up beside a corvet and dust it in my 1996 sts that would be somthing. im an adict to i love this car.

chevyorange
06-08-06, 03:15 AM
Update. I went with a rebuild myself. I did end up in addition to head gasket problems on both banks, having a cracked head and major oil leak straight onto the exhaust.

I searched extensively and went with a $3500 rebuild from US Engine in Kent, WA. 7 year 70,00 mile warranty. The thing has POWER. It is hard to keep the wheels straight under full throttle! While it was out I had a new starter, alternator, power steering pump put in. Also had front suspension parts replaced, tightened up, and boy, she drives straight (except for torque steer).

I hope as more N*s are on the road we'll see cheaper options. I'm happy with my decision now, the car mechanically is very, very solid and tight. It actually scares me from a roll how quickly it gathers steam, even on a steep, long hill by my house, (Highway 18 for those who live near Federal Way). I feel if I wanted to, I could start at the bottom and literally while climbing the hill quickly reach top speed in 3rd whatever that is... OD might slow the acceleration but it is a thrill to take just about anything on a hill like this - it seperates the men from the boys! The Northstar feels like it is on flat ground going up this hill - literally effortlessly climbing it.

What a car this 1994 STS is. It is expensive to fix if something gives, but it is a marvel to me. I can only imagine a RWD STS-V.

Cheers, fellas!

MARK99STS
06-08-06, 11:26 AM
They are forged

The rods are forged,but the pistons are cast and not the best. I would not run more than 7 or 8lbs of boost or your ringlands will probably crack.
There are slightly oversized forged pistons and forged Eagle rods available for the N* at different compressions available. The crank is cast but can easily handle up to 600hp.

chevyorange
06-08-06, 11:33 AM
I've never used a power adder - but is nitrous oxide basically the same stress factor on an engine as a supercharger? If not, what do the internals look like on a stock/rebuilt N* to handle a 50 or 100 shot of NO2?

auroradude
06-09-06, 04:34 PM
nooooooooo a supercharger has the power going through it all the time. At least get up to 3rd gear 4k rpm and floor the gas then activate the nitrous. I think if its under 4000 you could blow something.