Is GM's Northstar V8 any good??

davefr wrote: d> I'm curious where the Northstar V8 fall in terms of overall d> performance and reliability. Does this engine have a good reputation d> (like GM's 3.8) or is it a dog? (like GM's 3.4)

d> Does it have piston slap?

d> Is there much in the way of aftermarket mods available? Any good d> forums that talk about this engine?

The Northstar has been around for a little over a decade now. It's the direct descendant of the 4.5 and 4.9 Caddy engines that were supposed to remedy the gutless (for a big Caddy, anyway) 4100.

It's a high revving aluminum engine and as such is extremely sensitive to coolant maintenance. In 1996 they came from the factory filled with the 'orange' DexCool which almost eliminated maintenance, at least up to 100K or so.

The 4.6 liter has two versions, the 300HP in the Concours, STS and ETC, and the 275HP in the other Caddies. The Aurora had the baby NS at 4 liters. Their potential is mostly at higher speeds.

I'd say it has a good reputation, although repair costs are a bit on the high side, unless you tackle them yourself.

There is not a lot you can do to it, maybe opening up the exhaust a little bit. For earlier models (OBD-I) you can get a "chip" but basically what it does is it gets rid of the speed limiter. A supercharger has been in the works for quite awhile. Some guys on the forums below did put their Caddies on the bottle (NOS).

These are two excellent forums dedicated to contemporary Cadillacs:

and Check'em out.

-Bela

"Northstar" is actually GM's attempt to move to a truly corporate-wide powerplant (something Chrysler and Ford did during the 1950s) rather than have each division crank out engines that have overlapping capabilities. GM has come a long way since the days when Buick, Olds, and Chevy all had 350 CID engines with no parts that interchanged among the 3, and there were 3 455 CID engines (Buick, Olds, Pontiac) plus the Chevy 454 and the Cadillac 472, again with no interchangeable parts. But there is still some overlap- the Buick 3.8 is so much better than the Chevy 3.4 that there's really no need for the latter to exist other than to meet sheer production demand (and the fact that Chevy has forced their inferior designs down GM corporate's throat for decades). A corporate engine design would finally cure that, but Northstar hasn't really spread beyond the Cadillac and Oldsmobile lines. Rumor is it WILL find its way into more cars in the future and will expand to more than its present 2 sizes. Its an excellent engine with no recurrent problems that I've heard of. The downside is that it is rather expensive to work on when it does need work, because it is very compact and rather complicated compared to, say, a Buick 3800 or Chevrolet LS-1.

I'm sure there are forums, but since the unmodified engine hauls the big-honkin' Seville down the quarter mile in the 14-second range, the aftermarket doesn't get much demand for improvements to it... especially given the demographics of the typical Cadillac buyers.

"davefr" wrote

In some respects it has a great reputation. Very reliable when it comes to major mechanical components, lots of power out of small cubic inches, very quiet engine.

It has it's problems though. Engine oil leaks are a common complaint. It also can have problems with head gaskets, and/or head bolts pulling the aluminum threads out of the block. It's very expensive to repair....as any repairs on it are labour intensive. As an example....two common repairs that I've done many of...head gasket replacement with installation of thread inserts in the block..and lower case half seal replacement....will easily cost in the 5000 dollar range. Labour time for these repairs is between 25-32 hrs.

No, but it does have oil consumption problems. The purists will say that this is normal for a high performance engine, which I can agree with, but the Cadillac customers wont put up with it. At present, GM has us performing carbon cleaning treatments that are an attempt to free up sticking rings......and if that fails, there are updated rings for the late model engines.

Check out the forums that one of the other posters mentioned. I've heard that some places can get over 1000 hp out of these engines.

Ian

"Kruse" wrote

Yeah, I've replaced starters on these engines.

Takes about 15 minutes to get to this point:

I think the labour time is between 1 1/2---2.0 hrs.

Ian

Holy smokes - The starter is under the intake?! Wow.

Piston slap and high oil consumption are things that were common in the

30s, disappearing by the 40s, and GONE by the 1950s. But they're back today thanks to more and more stringent fuel economy requirements. One of the best ways to get rid of friction in an engine is to decrease ring tension, increase piston-to-bore clearance, and shorten overall piston height. These steps also increase power output somewhat, but the down side is that the greater clearances and lower tension leaves less margin when things start to wear, so engines get noisy and start slurping oil sooner than they did 20 years ago. Most modern engines don't have serious troubles (in fact I'd say MOST don't), but there are a few out there where its very clear that the manufacturers REALLY pushed the envelope and in fact went too far. The Ford 5.4 is one example (both oil consumption and piston slap). So is the Chevy 3.4 (mainly piston slap). This is the first I'd heard of the problem with the Northstar but it certainly doesn't surprise me. Changing the ring design and/or material sounds like a perfectly reasonable fix. Too bad it requires a complete tear-down... :-p

I'd heard where the starter was located on the NS, but I'd never actually seen a picture. Wow, they'll do ANYTHING to save space these days, won't they?

Doesn't it also have a liquid-cooled alternator that is plumbed into the engine coolant system? Or am I thinking another engine....?

Yuck! Guess i'll be staying away from anything with a Northstar V8. That just doesn't look like any fun at all.

Eddie

Its not as bad as it looks. You want 300+ horsepower in a package small and light enough for transverse-mounted FWD, you pay the price.

And besides, compared to working on some imports, thats a walk in the park.

Eddie A wrote:

"Steve" wrote

They say that there a few other reasons for placing it there. No room underneath the engine, due to the placement of the exhaust crossover pipe which runs under the engine oil pan. The exhaust crossover pipe "cannot" be removed until the transmission is out. Lousy design, but necessary to to the space restrictions. Actually, the starter is nice and cosy sitting under the intake....no moisture, dirt, and/or all the road crap. It's easy to get at, and is almost always clean when you get to it.

They only had those for a couple of years. They are nasty to get out. The entire rad/condensor/fans have to come out to get at it. The regular alternators are tough to get at too, but again, once you have done a few....it's not that bad.

Ian

"Steve" wrote

We do everything "but" replace the rings if we can get away with it. Re-ringing a Northstar under warranty time constraints is tight. Apparently, this new ring design is actually an old ring design. They have brought it back.....just for the occasional Northstar that uses too much oil.

It has a stepped second compression ring...other then that, the other rings are the same.

Ian

Goodness, that *is* an old ring design, which was popularly and widely used up through the 1970s as service replacement rings to control oil burning. The stepped ring twists slightly in the groove on the downstroke, which causes its corner to do the cylinder wall scraping rather than its edge. The risk, of course, is increased ring land and cylinder wall wear, but the degree to which this occurs is highly dependent upon bore and piston material, engine rod ratio, etc.

DS

"Daniel J Stern" wrote

Yeah, I guess like so many other things, it's a compromise. I did one of these re-ringing procedures a few weeks ago, and while I'm sure the stepped rings will help....there were other problems. Two head bolts on the rear head had pulled the aluminum threads out of the block, which was causing an oil leak from the head gasket....plus there would be a certain amount of block distortion with 20% of the head bolts having no clamping load applied to the cylinder head. Cadillac has come up with a revised head bolt torque spec to "supposedly" address block distortion and thread pull.

The rings on the two middle cylinder...rear bank....were quite literally seized in the ring lands....just all gummed up with carbon. And this engine only had 45K klms on it. Again.....most of these Cadillac owners just putz around town with these engines. One recommendation from a very knowledgeable source on these engines is to perform

2nd gear full throttle accelerations from 50 mph up to 70 mph and then release the throttle and coast back down to 50 mph....repeat. Apparently this will help to keep the rings free from too much carbon buildup. Obviously, this is not really something I can recommend to customers. I can just see all the Northstar customers doing 2nd gear blasts around the city.

Ian

My one friend who owns one (his wife's car) takes it out to the dragstrip every few months. He likes clicking off EXTREMELY repeatable

14.xx - second runs and watching the "rice boys" cursing him for being so consistent (bracket racing, y'know).

He could've smashed the thing the first time he ran it and it turned a better time than his Ram SS/T. Then he tweaked (some more) on the Ram, so its now faster than the Caddy... BARELY. :-)

I've got the 4.0L Northstar in a '99 Aurora. Seen many incidences of this head bolt problem discussed on the IATN list. Is there anything I can do as far as maintenance to prevent this happening to my engine, Ian? Or is it mostly a problem with the 4.6L engine? Thanks.

Garrett Fulton