94 Northstar overhaul

[jlinde]

I just started with going through a 94 Northstar for a 94 STS. One cylinder was low on compression

so I took the heads off ( probably an exhaust valve). All the head bolts came off without

any problems so I plan to put new ones back later on without timeserting. But, on the which I suppose original bolts threads there is some kind of chemical -loctite or something. When I read the 93 and 94 shop manuals for head bolts they only mention oil on the washers when fastening the heads.

The head gaskets are (on 2 engines that I took apart) GOETZE (german brand??) .

Does anybody know what to use on the threads for head bolts to protect them from corrosion

and timeserting?

/Jan Linderholm

[JimD]

The locking material would be already installed on new head bolts; and you must use new head bolts.

And to take a chance on NOT Timeserting is a poor gamble.

Protect your time and labor investment; Timesert the block bolt holes, use OEM head gaskets, and new OEM bolts.

[jlinde]

The locking material would be already installed on new head bolts; and you must use new head bolts.

And to take a chance on NOT Timeserting is a poor gamble.

Protect your time and labor investment; Timesert the block bolt holes, use OEM head gaskets, and new OEM bolts.

[jlinde]

Well I have ordered new bolts and gaskets from FELPRO. Are those not good enough - I mean they are used in millions of repairs. About the timeserts needed or not needed - I suppose they are better of course than just aluminum but the cost here in Sweden is totally $700 for just the parts. In my case it is a matter of money but if I do the timesert I should maybe also check the rod and main bearings meaning new gaskets and bearings and connecting rod bolts (according to shop manual).

/Jan Linderholm

[Ranger]

The lower end is very strong. Don't touch it. Our old Guru (a GM powertrain engineer) said once you pull the bolts, you are taking a chance of a future failure if you don't Timesert. I agree with JimD. Always Timesert.

[BodybyFisher]

You make this statement:

"All the head bolts came off without any problems"

That is not the criteria as to whether or not you timesert your block. Once the bolts are disturbed, you timsesert them.

You talk about FELPRO gaskets, I am sure they would work, but who knows, do you know if FELPRO has updated them? I am sure that GM has updated their gaskets as the engine has been developed. BE SURE you use new OEM bolts they stretch when torqued. Be sure you understand the torque angle method of tightening the head bolts and that you have the correct tools.

[KHE]

When I did the job on my '97, the shop manual did not mention using oil on the head bolt washers so I didn't. I would be inclined not to use oil on the head bolts as I'd be concerned about it conaminating the threaded holes and interfering with the bond of the threadlocker on the head bolts. If that happens, they will back out and you will be doing the job all over again.

I would not recommend putting the heads back on without timeserting the holes - a few on this board haven't used timeserts and had to do the job again in 12,000 miles. Not worth it in my opinion.

The head bolts do not stretch during installation - they are not torque to yield bolts. New bolts MUST be used upon re-assembly. Do not use anything to keep them from rusting - that will interfere with the threadlocker. The M-6 bolts in the chaincase area are OK to re-use as there is not any factory applied threadlocker on them. When timeserting the hole, appropriate lube must be used on the drill and the tap. Timesert recommends WD-40. Once the head bolt hole is drilled, it must be blown out with compressed air - I used a nozzle that would reach all the way to the bottom of the hole and a shop vac to suck up the shavings while blowing them out. Tap the hole and repeat the cleaning process. Then spray brake cleaner down the threaded hole to remove the cutting oil and blow it out. A slight amount of installation oil (included with the Timersert kit) is applied to the installation tool and the insert is installed onto the installation tool. Then, a small amount of threadlocker (again included with the Timesert kit) is applied to the lower portion of the Timesert. The insert is then threaded into the block until resistance is felt in the driver, keep tightening the installation tool until it is easy to turn. The Timesert is now installed. Timesert has a downloadable video on their website. The instructions MUST BE FOLLOWED TO THE LETTER for a successful repair. Do not be temoted to shortcut the process. Once all the holes are Timeserted, use brake cleaner spray and compressed air to remove the driver oil from the hole.

Have you tried www.gmotors.com for OEM parts such as head gaskets, bolts, seals, etc? I think they ship worldwide and have very competitive prices. Also, it would be worth checking out the timesert website and asking them if they will ship worldwide. The kit with 10 inserts (you'll need to buy another 10) is about $380. It includes the drill fixture, thread locker, special drill bit, special tap, installation oil, and 10 inserts.

Let us know what you find as far as the cause of the low compression. Hopefully, it is just an exhaust valve so you don't have to re-ring it.

[BodybyFisher]

I thought the guru said the bolts needed to be replaced because they have a predetermined stretch and once used that is gone. This is news to me Kevin.

[BodybyFisher]

I found this, here >> http://caddyinfo.ipbhost.com/index.php?sho...mp;hl=stretched

I think the guru wrote it:

The Northstar head bolts are not torque to yield fasteners. They are recommended to be used only once since they are coated with a microencapsulated thread locking agent that acts as a thread lubricant during assembly and a locking agent once the bolt is installed. There is no practical way to reapply these coatings on the threads and under the head of the bolt so new bolts are recommended when the head must be removed. Otherwise, the bolts themselves are fine.

Torque to yield bolts will stretch permanently when they are properly tensioned. If you measure the bolt, install it and then remove it you will find that it is now longer even when not under load. Those types of bolts cannot be reused as they keep stretching and then break. The Northstar head bolts are not like that despite common rumor.

The Northstar bolt tensioning is spec'd as a torque and angle. Torque and angle provides a much more accurate means of tensioning a fastener compared to a pure torque spec. Just because the fastener is spec'd for torque and angle does NOT mean that it is a torque to yield fastener.

Torque and angle specs even work great on studs as the torque and angle spec, once properly developed, is far more repeatable and accurate than pure torque. Ask ARP.

Any one who thinks that the Northstar head bolts stretched and caused the head gasket to fail is nuts. They didn't measure the bolts originally at the factory so how on earth could anyone suppose that the bolt "stretched" (since they didn't know how long it was originally...) I think they dreamed up this idea of the bolts stretching to explain something and posted it as fact

[BigCat83]

Jan; Timesert that block! You are setting yourself up for failure if you don't!

Good luck.

[jlinde]

OK, thank you for all info and wisdom - IT WILL BE TIMESERTED -

The STS is from Switzerland and imported to Sweden with a shot engine

(spun bearings) and the replacement engine is from a wrecked car

with 100000 miles together with a remanufactured 4T80. The STS is

newly repainted white pearl and has no rust at all (I do not think they use

salt on the roads in Switzerland as here in Sweden).

It is more of a hobby for me to repair it as I am retired and have all the manuals.

It will be used all the year round which is not the case with my white pearl

93 Eldo TC which is for summer only (53000 miles).

/Jan Linderholm

[KHE]

I found this, here >> http://caddyinfo.ipbhost.com/index.php?sho...mp;hl=stretched

I think the guru wrote it:

The Northstar head bolts are not torque to yield fasteners. They are recommended to be used only once since they are coated with a microencapsulated thread locking agent that acts as a thread lubricant during assembly and a locking agent once the bolt is installed. There is no practical way to reapply these coatings on the threads and under the head of the bolt so new bolts are recommended when the head must be removed. Otherwise, the bolts themselves are fine.

Torque to yield bolts will stretch permanently when they are properly tensioned. If you measure the bolt, install it and then remove it you will find that it is now longer even when not under load. Those types of bolts cannot be reused as they keep stretching and then break. The Northstar head bolts are not like that despite common rumor.

The Northstar bolt tensioning is spec'd as a torque and angle. Torque and angle provides a much more accurate means of tensioning a fastener compared to a pure torque spec. Just because the fastener is spec'd for torque and angle does NOT mean that it is a torque to yield fastener.

Torque and angle specs even work great on studs as the torque and angle spec, once properly developed, is far more repeatable and accurate than pure torque. Ask ARP.

Any one who thinks that the Northstar head bolts stretched and caused the head gasket to fail is nuts. They didn't measure the bolts originally at the factory so how on earth could anyone suppose that the bolt "stretched" (since they didn't know how long it was originally...) I think they dreamed up this idea of the bolts stretching to explain something and posted it as fact

Yes - the guru wrote that - I remember that post.

[zonie77]

You might watch ebay for a used timesert kit. You would probably have to get the inserts from timesert as most people sell the kit used without any inserts. That would save you about half the cost but not all sellers are willing to ship out of the US.

I'm sure some blocks have stayed strong enough to retorque the head bolts but the possibility of some weakening of the aluminum is high. There have been people on the board who had failure with blocks that looked good. If you are in no hurry you could try it. If you get a failure then you could get the timesert kit and install the inserts. The torqueing is at the beginning of reassembling the engine so you wouldn't lose that much work or time.

If the engine is assembled but not run the head bolts and gaskets are still useable. You would not have to replace them.

If you need the timeserts you might consider the other insert set (commonly referred to as Norm's). You can find that on ebay also.