: Maintaining Northstar Engines *A must Read*



nerisauto1
12-23-03, 01:28 AM
click and paste http://www.babcox.com/editorial/us/us100232.htm

elwesso
12-23-03, 11:04 AM
Great information... Could you post that link into the FAQ section in the suggestion forum????

Sinister Angel
12-23-03, 08:09 PM
Wow! Good info
Now is it just me, or is it dumb of GM to make the liners non replaceable?

elwesso
12-23-03, 08:55 PM
The way I see it, if they made them replaceable then it would be ONE MORE thing to fail on that engine!!! And cause more hardaches!!!

Sinister Angel
12-23-03, 11:40 PM
The way I see it, if they made them replaceable then it would be ONE MORE thing to fail on that engine!!! And cause more hardaches!!!

Doesn't seem to be a problem in the diesel community...

zonie77
12-23-03, 11:56 PM
I don't think cadillac has any intention of repairing liners. They don't care if it needs a liner after a piston failure, they throw a new block in.
The N* we pulled apart recently had 130,000 miles on it and still showed crosshatching. If you don't have a catastrophic failure the block should go 200K+.
I think Caddy made a reasonable decision and it's probably more reliable and easier to manufacture than removable liners.

A diesel is another matter entirely.

black45
10-29-04, 05:31 PM
i have a 1995 sts and i have got gas in my oil i may have to have a motor do you know of any body that has one for sale

infin1ty
10-29-04, 08:01 PM
The 4.9L has replaceable liners, and I guess very few have been replaced.

BeelzeBob
10-29-04, 09:11 PM
i have a 1995 sts and i have got gas in my oil i may have to have a motor do you know of any body that has one for sale


Gas in the oil....???....sounds like you have an injector stuck open. Pull the plugs and turn the engine over and see which cylinder it is.


BTW.....the Northstar liners are cast in place and are not removeable or replaceable....but.....they are designed to be overbored by as much as 1mm if necessary. BMW and Mercedes use either a Nikasil or exposed silicon (Vega) surface finish on their bores so they are far from serviceable....

The reason that the Northstar has cast in place cast iron cylinder liners is several fold....one, it makes the engine capable of being run without coolant, with the help of the loss of coolant limp home mode, with no engine damage. Other cylinder wall surface finishes are not capable of that. Two, casting the liners in place allows the bore centers of the engine to be closer together (the liners can be thinner and positioned closer together) as the siamese area of the cylinder bank reinforces the area between the cylinders. Closer cylinder bore spacing is important in packaging a V8 in a TFWD car. Three, as mentioned the liners are thick enought to allow a 1 mm overbore. Buy casting them in place the engine can be re-manufactured easily as required. Machining the individual liners as with the 4.1/4.5/4.9 takes special equipment.

As noted, many Northstars have been apart on this forum and all have noted that the cylinder walls and pistons are perfect, with the original factory honing pattern still visible, with well over 100K on them. The cylinder liners are a very hard cast iron and honed for oil retention that makes the liners wear very very little and last virtually forever. Most any forceable problem that would cause a rebore would likely wreck the block in other areas so cylinder wall refinishing has never been an issue in the field to my knowlege.

dkozloski
10-30-04, 12:51 AM
Just because the liners are cast in doesn't mean they can't be replaced if they're going to make your wife a widow and your house into a dung heap. There are quite a few after market cast iron sleeves that can be installed after a minimal rebore. Some only require a 0.060-0.080in. rebore, the sleeve is pressed in, and then bored to size. This is the kind of repair you would do after a catastrophe in one cylinder. It probably would not be a good deal for a race machine but works fine for a daily driver.

majax
10-30-04, 01:24 AM
"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."

so according to them Northstars done last very long.

BeelzeBob
10-30-04, 07:17 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."

so according to them Northstars done last very long.



UHHHH....Duhhhh.....maybe "they" are wrong....?????? LOL LOL LOL

The article certainly blew it when "they" said that the liners are not serviceable, didn't "they"...???

dkozloski
10-30-04, 10:31 PM
bbobynski, are the sleeves corrugated on the outside like the sleeves in a ZL-1 Chevy? How thick are they at the thinnest point? Do they have a flange at the top? I have seen some sleeved Cosworth Vegas that were used in midget racers that had phenominal power and dependability. I'm with you. Just because some armchair expert says something doesn't make it so. Sometimes the repairs people do make the purists cringe but they still work. I've seen cracked blocks repaired with JB Weld and steel wool driven in the crack with a screwdriver. I've seen frozen engines with the water jacket pushed out a quarter of an inch repaired with Devcon, sheet aluminum and Cherry-Max rivets. These crimes against machinery lasted for years. Resleeving, or more correctly a sleeve repair of a Northstar sounds to me like no big deal, except like you say that there is seldom need for it because the original setup is so robust.

RLLOVETT
10-31-04, 01:00 AM
Here's one with 28x,xxx on the clock...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6147&item=2497688598&rd=1

majax
10-31-04, 04:35 AM
That is a crap load of miles, my Honda Accord will probably not last that long.

My STS better last that long :D

BeelzeBob
10-31-04, 01:09 PM
The cylinder liners have a machined pattern on the OD to lock them into the casting. There is a land at the top to provide more head gasket bearing surface. Even the land has a special series of grooves machined in it to lock it into the aluminum. There was a lot of development work that went into the machined finished on the OD of the liners to make sure that they stay put during the engine's life and the extremes of temperature and thermocycling. The liners are 3-4 mm thick. I forget the exact dimensions off the top of my head....

The 4.0 liter Aurora (Northstar) engine that was produced for the Oldsmobile Aurora had an "as cast" surface on the OD of the liner. It was a special finish created in the spin casting process for the liners developed for that application. Since the 4.0 had smaller bores it had more room between the bores so the exact liner OD was not as critical so the as cast dimension and finish could be used. It simply avoided having to machine the OD of the liner for the 4.0 as a cost savings. No real difference at all in the performance of the liner retention or anything between the machined and as cast surface on the OD.

As an interesting tidbit, there are a number of 4.0 engine in service in 1995 Aurora's that have a complete aluminum deck surface....i.e...the aluminum of the cylinder liner "muff" extends over the top of the liner so that the deck is all aluminum and the top 1 mm or so of the cylinder is aluminum. That was the original developement intent for the Aurora and Northstar to avoid having to machine a bi-metal deck. When the block is decked on a conventional Northstar the cutter is cutting cast iron of the liner and aluminum of the deck and liner surround or muff. This is hard on the cutter so that it doesn't last very long... A cutter that cuts only aluminum can be made to last forever with diamond inserts. But diamond inserts will not cut the bi-metal surface. So, the 4.0 went into production with the all aluminum deck. It was dropped and the 4.0 went to the construction you see on the Northstar with the liner sitting at the top of the deck near the end of the 95 model year. It was just too hard to control the height of the liner with the aluminum over the top of it in the die when the block was cast. Nice idea, just didn't pan out. It cost more in scrap blocks from the casting process than replacing the cutters all the time. So, it wouldn't be too uncommon to see an Aurora block with aluminum over the top edge of the cylinder liners.

It would be relatively easy for a good engine shop to completely bore the iron liner out of the aluminum surround and press a new one in if the need demanded it. Just a case of a specialty engine that cost more to replace the block than to machine and fit a new, aftermarket liner. This kind of thing is done very frequently in the collector car market where certain specific blocks are extremely rare and need to be reclaimed. Not that hard to do, really, and very effective. Just costly for an everyday beater. I have even seen a Northstar block with the free standing cylinders completely machined away and the 4.9 style wet liners fitted into the pilot bores in the bottom. It ran fine. Lot of machine work and custom liners but it worked great. Anyone says that something "can't be done" should look around a little more.....LOL....

My favorite backyard repair was an old Briggs and Stratton 5 HP that I raced on a gokart back in the very early 70's. I was racing it on a literal shoestring being in high school and ended up breaking the block completely in half due to an extreme overbore (vey thin case left) and a broken rod. The cylinder portion of the block broke off the crank case. Since it was a nice clean break and I had no other engine and no $$$$ I "glued" the halfs back together with JB Weld, assembled the engine with a new rod and then reinfoced the engine with two large pieces of threaded rod from the engine mounting plate up to a steel "strap" that set across the head bolts. Just clamped it together with the two pieces of threaded rod!!! It ran for several races like that with no problems. If you look at Kart racing today they actually sell a reinfocing kit like that for the NHRA junior dragster engines!!! I'll lay claim to having the first one. It wasn't as pretty but it worked.

Sinister Angel
11-25-04, 06:41 PM
Bump because this thread should be stickied

Pjs
11-26-04, 12:40 PM
As noted, many Northstars have been apart on this forum and all have noted that the cylinder walls and pistons are perfect, with the original factory honing pattern still visible, with well over 100K on them. The cylinder liners are a very hard cast iron and honed for oil retention that makes the liners wear very very little and last virtually forever

I got out the digi cam last night...this is #7 cyl wall, 137K miles

96 STS
11-26-04, 12:49 PM
WOWWW!!! That is an AWESOME site to see!! Not too bad for 137K.

If only all engines were built so tough. But...then again, if ALL engines were built so well, they wouldn't be able to sell so many cars.

Pjs
11-26-04, 01:08 PM
Still pretty hard for me to believe sometimes, given the amount of 350's and RB block mopars that I've rebuilt and not one EVER looked that good.

dkozloski
11-26-04, 03:44 PM
The picture may be just a little misleading. The major share of cylinder wear occurrs at the very top of ring travel not the bottom which is shown in the photo. I would be interested in seeing and measuring the ring ridge before passing judgement.

Pjs
11-27-04, 12:29 PM
The picture is not misleading at all. The discussion was about the original hone marks being visible @ well over 100K miles. Granted, the most wear does occur @ the top of the cylinder, but your looking at over 1/2 of the piston travel here as the piston is bottomed on the head. I hardly think your going to see these hone marks where they are and have a ridge at the top.