Alternative to Time Serts?

[jking220]

I bet if the guru was still here he would be all over this product... In a good way... It is one of those... "I wish I had thought of this first"

I agree that studs are much more "bullet-proof" than bolts, but what engineering has gone into these studs? Is the geometry copied directly from the factory bolts? Is the material/heat treat the same? These are "turn to torque" bolts if Im not mistaken, so the ability of the bolt to stretch the right amount means everything about clamping force, and the ability to keep that clamping force over a wide range of pre-load forces (ie different temperatures with different materials).

I dont know that I would be as worried about pulling a bolt after the repair as I might be about hurting something else due to too stiff of a joint.

JMO.

[KHE]

after getting things disconnected I've come to the conclusion I'm better off getting rid of this problem. I've put all back together and I'm car shopping now. After 40 years of owning cars this is by far the worst I've ever owned. I never did get the engine out. But I did enjoy the car for 10 years. Cessnatech.

We never heard how your diagnosis went. I am assuming you confirmed a bad head gasket either by pressurizing the cylinder or testing the coolant for combustion gasses?

[Jan Olsson]

You all seem to forget the fact that the guru always said that the main reason for the Northstar engine to suddenly overheat is due to a neglected coolant system. In the cases that the system was well maintained then we can start talk about bolts suddenly coming loose. I believe that most of the people having bolts with stripped threads are experiencing threads that were ruined when dissembled.

The main problem is the head gasket design that was changed on 2004 (?) and in the cases of real loose bolts porosities in the casting.

He also always stated that the Northstar engines doesn't have more head gasket problems than any other car..it is the most common "major" problem with this engine.

I believe he had the figures right

He also said that he had never had any problems with Timserts.

There was no reason to have inserts from the factory in the block from an economic point of view since the original threads does its work as they should (again except from the unfortunate ones with porosities in the blocks). It is when you remove a head you wish that there were inserts since the threads are unusable after removal in most cases.

The Timeserts were extensively tested to be a bulletproof repair and I believe that there must be extremely rare that they don't work as they should if they are correctly mounted.

I know that there are a few strong voices on the internet claiming Timeserts are worthless, probably the same people having "bad" blocks or having done a bad Timesert job.

My point is that I think they did the right thing from the factory, stuff happens and the FWD layout makes it an expensive and somewhat difficult repair. What if you had to do it on a RWD vehicle? I bet most of us here wouldn't think of it as a big deal. Annoying yes, but not a big deal.

When I had the rear head of on my 1993 STS the guy who machined the head (a burned and cracked exhaust valve did some nasty things with the seating surface) was impressed about the head design since the cloverleaf was done in the casting process. They usually machine the heads to do that design. He also had a very large amount of heads from BMW’s of all kinds and sizes lying around. Many of them were melted or warped (you could se it without having to measure them...) Any carmaker has their problems.

Even if all the owner reported faults in the JDPower results for Cadillac’s were from overheating engines they still do a very impressive reliable car since they always places them self on the top 5 wouldn't you agree?

I would try another insert only if the block seemed crystalized in the thread holes because then the only possibility would to switch blocks.

[Jan Olsson]

Thanks for the info KHE, I'm still getting things disconnected and trying to identify where things hook up. Also I take it you are not sold on the stud kit v. time serts. I've worked as a machinist and aircraft machanic and have had experience with heli coils. My main worry is doing the timesert and the threads still pulling out. I'll keep you posted. Cessnatech

Correct - I am not sold on someone's stud service... I have Timeserts in my '97 Seville - for 38,000 miles, they have held up just fine. Heilicoils are not to be used to repair the head bolt holes in the Northstar Engine. Heilcoils will pull out upon torquing the engine the heads down. If you look at the Timersert web site, you will see the "Bigsert" description is "for when Helicoil fails"...

I like the Timesert because that is the only thread repair that was tested/validated by GM to be an approved repair. Any other methoid and YOU are doing the validation at YOUR expense...

Couldn't have said it better

[Jan Olsson]

The Guru had a debate over what precisely was the likely reason why time-serts were needed after heads are removed. He stated that the impression of pulled head bolts was due to removing the bolts in the first place, which where locked into the block. When the bolts are removed the threads would strip and thus create the impression that they were deteriorating inside the block. He didn't state that this would be the case at all times, however, he did say that when a head gasket needed replacement the likely cause was deterioration of the head gasket rather than pulled head bolts. Again, he had quite an extensive debate over this issue and went into detail as far as what precautions GM took to coat the bolts and to create a protected pocket that would seal/shield them from antifreeze. He also stated that the most likely reason why head gaskets deteriorated was due to age, stress and/or neglected antifreeze. He also said that the more miles an engine has the greater likelihood that bolts would become even more difficult to pull as over time they actually become locked into place. Anyone who has done a head gasket job probably remembers that the head bolts are quite long, which is well beyond what would be required to withstand the maximum pressure that could be generated by the Northstar. The Guru stated that GM deliberately made the head bolts longer to insure they could withstand the maximum pressure and not pull, particularly in an aluminum block.

I wouldn't know if he would have changed his point of view since his original assessment of this issue, but I distinctly remember that he did state that head gasket failure was most likely caused by the head gasket itself and not pulled head bolts. I know that there are some that insist that anytime a head gasket blows it's due to pulled head bolts--however, chances are that pulled bolts is not the cause.

If anyone remembers something different, please let me know. However, I distinctly remember what the Guru said about this issue.

That is pretty much exactly what the Guru said... I wish he was still around to discuss and debate this further... Some interesting empirical data around Northstar head gasket problem is starting to come in:

1) About 75% of the problem occur in the tight span of 1997/98 and 99 model years. The frequency drops DRAMATICALLY in 2000 when GM switched to longer head bolts and it drops to zilch in 2004 when GM switched to LS1 style "long and coarse" head bolts.

2) Who has ever heard of an LS1 head bolt or headmaster fail? Why? These engines have been out there almost as long as the Northstars and yet the coarse head bolts on these motors seem to tolerate one torquing after another into aluminum blocks without pulled threads...

3) Older Northstars (93-96) seem to be almost as good as the 2000-present units... if this is a coolant issue these should be the worst of the bunch... but they aren't.

4) There are lost of "over" maintained coolant systems out there with failed head bolts too... my 2002 hasn't failed... But my car gets new Dex every other year REGARDLESS of miles... If the head bolts let go it won't be the coolant on my car.

5) There are even more Northstars that are just fine still running on the 10 year old factory coolant (One is a friend of mine)

6) The locker that is used to "glue" in the timeserts is also proving to be problematic and there is lots of data around serts that come unstuck and fail. The sert has two clamping surfaces (inside and outside) and is an additional failure point.

I really like the idea of these studs... as I understand them they use a thread pitch that is at least as course as the "better" LS1 bolts PLUS they are longer and have a greater diameter. (win win win!)

The only down side is that you can't remove the heads in the car anymore... but you can't do that anyway...

I can't see any down side to this product.

Stronger, Better, Faster... Smarter!

1) A head bolt is always experiencing a dynamical load. A long and small bolt is always better than a short big bolt from a dynamical load point of view. In this way they probably reduced the dynamical loads on the head gasket and prolonged the life of it. The coarser thread is probably to reduce the risk of real head bolts pulling due to a porous block.

2) A coarser thread can also withstand disassembly better than a finer one. There is also a question about how big maximum force is expected on the head bolts. The older LS1 engines had five bolts per cylinder right? The temperature creates an incredible load on the head bolts. The operating temperature on those could differ? Head gasket design etc. The Northstar engine has its “Limp-home” feature and to withstand the forces from the heat at 250+F the head bolts have to be highly strung to say the least. Perhaps the LS1 engine doesn’t have that feature?

I mean that a “low clamping force” joint doesn’t ruin the threads when dissembled. Think of all the other bolts on the Northstar engine. You never Timesert them, not even use Helicoils. Just because they aren’t highly strung.

3) You got me there J Some change in the casting process perhaps? That is of course not acceptable but they did fix it after they discovered it wouldn’t you agree? It takes some time before they see how changes work “in the field”

4 and 5) Coolant system service is your best bet to avoid head gasket failure. Not every one fails even if the coolant is never changed. Driving conditions like many cold starts and hard driving would accelerate thermal cycling on the gaskets.

6) Why problematic? The Timeserts if done properly are seated against the head. That and the threads hold them in place. The liquid thread locker is only to prevent turning of the inserts.

The bigger the diameter the less stress on the treads. If you have the same material you would expect failure on the inner thread before the outer one goes. Since the Timesert is made of steel that connection is stronger than the original one and since the Timesert has a much larger diameter than the original one it is also much stronger.

The studs are longer which is good. The larger diameter on the other hand could do the dynamical load variation larger if not the ratio length/diameter is kept. That could be bad for the head gasket.

[Jan Olsson]

All modern aluminum engines use torque-and-twist bolts for the cylinder heads. Torque-and-twist bolts are actually tension springs. The tension on each bolt is adjusted by turning the bolt a specified angle after the bolt head contacts the cylinder head; the angle with the thread pitch gives the stretch distance, and the bolt alloy and thickness with the stretch distance gives the clamping force.

With this procedure the internal fricition of the threads and the friction between bolt head and cylinder head won't be a problem at all. With only a torque wrench the real clamping force would differ greatly because the friction varies quite a lot. Main reasons are lubricants and differences from the theoretially correct geometry in the threads on the bolt and the hole.

[Jan Olsson]

Greg you said this

The only down side is that you can't remove the heads in the car anymore... but you can't do that anyway...

You lost me what do you mean, by, but you can't do that anyway

Yes technically you can remove the heads without pulling the engine or dropping the cradle. But once you pull a head you need to "sert" the block and while one or two brave soles have done this almost everyone agrees that it is easier to drop the cradle.

Plus head studs are just plain COOL...

Every racer will tell you that you cannot beat the pure clamping force that studs provide..

More clamping force with less stress on the block.

There are no difference in clamping size if you have the same size on the threads. The block will have the same stress whether you use bolts or studs.

The main reason of using studs is because you split a steel/steel connection not an aluminum/steel connection. This is good if your planning on doing several times of engine work on the heads. Just like Timeserts can be "dissembled" about 20 times.

[Jan Olsson]

To build an engine to JUST last 100,000 miles or LESS and potentially damage your reputation with the NEW and especially the USED car crowd, the ones that MIGHT just buy a NEW car one day by saving a few dollars on each engine is shortsighted and foolish.

Does anyone think there were ANY shortcuts on the 429, 472 or 500 cu in monsters?

I totally agree. They should have had the pressure casted blocks from the start and the latest head gasket design. But that’s evolution. It's always easy to know how it should have been done with facts from the "field" . Apparently it was an unforeseen mistake with the head gasket design etc. I simply don't feel that they made a cheap solution to start with. I believe that there were problems/combinations of problems that was not discovered until it was too late. It took time to fix it as expected since the problems revealed themselves after a couple of years. Then again not every Northstar goes KABOOM.. right?

The engines you mentioned was also heavier and oversized from a construction point of view

Don't get me wrong! I wouldn't be happier if a Northstar engine was indestructible and that is wat should be expected from a Cadillac. But I really don't think that it really is a big problem. Think of the JD Power statistics for instance?

[BodybyFisher]

Mine is a testament to that... KNOCK ON WOOD, LOL.... 121K and 196 degrees with daily WOT's.... tick tick tick tick tick BOOM......

[OynxSTS]

1) A head bolt is always experiencing a dynamical load. A long and small bolt is always better than a short big bolt from a dynamical load point of view. In this way they probably reduced the dynamical loads on the head gasket and prolonged the life of it. The coarser thread is probably to reduce the risk of real head bolts pulling due to a porous block.

2) A coarser thread can also withstand disassembly better than a finer one. There is also a question about how big maximum force is expected on the head bolts. The older LS1 engines had five bolts per cylinder right? The temperature creates an incredible load on the head bolts. The operating temperature on those could differ? Head gasket design etc. The Northstar engine has its “Limp-home” feature and to withstand the forces from the heat at 250+F the head bolts have to be highly strung to say the least. Perhaps the LS1 engine doesn’t have that feature?

I mean that a “low clamping force” joint doesn’t ruin the threads when dissembled. Think of all the other bolts on the Northstar engine. You never Timesert them, not even use Helicoils. Just because they aren’t highly strung.

3) You got me there J Some change in the casting process perhaps? That is of course not acceptable but they did fix it after they discovered it wouldn’t you agree? It takes some time before they see how changes work “in the field”

4 and 5) Coolant system service is your best bet to avoid head gasket failure. Not every one fails even if the coolant is never changed. Driving conditions like many cold starts and hard driving would accelerate thermal cycling on the gaskets.

6) Why problematic? The Timeserts if done properly are seated against the head. That and the threads hold them in place. The liquid thread locker is only to prevent turning of the inserts.

The bigger the diameter the less stress on the treads. If you have the same material you would expect failure on the inner thread before the outer one goes. Since the Timesert is made of steel that connection is stronger than the original one and since the Timesert has a much larger diameter than the original one it is also much stronger.

The studs are longer which is good. The larger diameter on the other hand could do the dynamical load variation larger if not the ratio length/diameter is kept. That could be bad for the head gasket.

1) Yes we agree... The short/fine bolts (which are the same BTW as problematic Quad-4s) are definitely an issue... It was good that GM changed to longer coarser bolts... The new studs are even coarser still... As an aside most of the best dealers are "upgrading" blocks by using Normsert or Timesert kits for a 2004 and new block and switching to the newer longer bolts.

2) No, all LS xengines have 4 bolts per cylinder and all are deigned to work in temperature ranges that EXCEED the Northstar... The LSx engines have one difference... Coarse long bolts from day one.

3) Lots of speculation here... you have to "harden" aluminum parts that will be exposed to silicate (green) coolants... It is not clear if the year after they switched to Dex they stopped the "hardening" step... and then started again in 2000... Or if the longer bolts did the trick... we will never know

4/5) Agreed... Mine gets new dex every other year (and I check the coolant monthly)... but that doesn't explain why there is neglected DEX is in thousands of all aluminum LS1 and LS2 engines with basically no head gasket issues.

6) 97/98/99 Timeserted engines are starting to fail now for a second time... and the glue that is to prevent the serts from turning... doesn't. The serts are comming out of the block during the repair... This makes for extra problems and basically "finishes" the engine.

The "big end" of the studs is the same diameter as the time sert... so the clamping and the termal issues will be the same... just one less mechanical joint to fail.

[Ranger]

I never disagreed with the Guru, you couldn't he always had the facts. But I felt they should have cast in steel inserts into the block and said so.

Mike, I believe they ARE cast in.

I bet if the guru was still here he would be all over this product... In a good way... It is one of those... "I wish I had thought of this first"

I'm sure he would, but I don't think in a good way. I can recall him having a heated "discussion" about this very subject with a Cadillac Tech. Some of you may recall it. That said, he was a loyal GM employee and a staunch Northstar defender. I don't think he would have admitted a problem even if it where true and he knew it.

[caddists97]

I think what he means is that it's near impossible to remove the heads in the car in the first place, although some with more patience than I have done this. It is very difficult and personally, I find it less time-consuming and easier to just pull the engine. I've done them all (48 cars) through the top, although if I have to pull another 2000+ Deville, I'm lowering the cradle. Too much crowding.

Im interested in using your product on my 97 sts do i have to pull the transmission with the engine if i pull it out the top.

[Jan Olsson]

1) A head bolt is always experiencing a dynamical load. A long and small bolt is always better than a short big bolt from a dynamical load point of view. In this way they probably reduced the dynamical loads on the head gasket and prolonged the life of it. The coarser thread is probably to reduce the risk of real head bolts pulling due to a porous block.

2) A coarser thread can also withstand disassembly better than a finer one. There is also a question about how big maximum force is expected on the head bolts. The older LS1 engines had five bolts per cylinder right? The temperature creates an incredible load on the head bolts. The operating temperature on those could differ? Head gasket design etc. The Northstar engine has its “Limp-home” feature and to withstand the forces from the heat at 250+F the head bolts have to be highly strung to say the least. Perhaps the LS1 engine doesn’t have that feature?

I mean that a “low clamping force” joint doesn’t ruin the threads when dissembled. Think of all the other bolts on the Northstar engine. You never Timesert them, not even use Helicoils. Just because they aren’t highly strung.

3) You got me there J Some change in the casting process perhaps? That is of course not acceptable but they did fix it after they discovered it wouldn’t you agree? It takes some time before they see how changes work “in the field”

4 and 5) Coolant system service is your best bet to avoid head gasket failure. Not every one fails even if the coolant is never changed. Driving conditions like many cold starts and hard driving would accelerate thermal cycling on the gaskets.

6) Why problematic? The Timeserts if done properly are seated against the head. That and the threads hold them in place. The liquid thread locker is only to prevent turning of the inserts.

The bigger the diameter the less stress on the treads. If you have the same material you would expect failure on the inner thread before the outer one goes. Since the Timesert is made of steel that connection is stronger than the original one and since the Timesert has a much larger diameter than the original one it is also much stronger.

The studs are longer which is good. The larger diameter on the other hand could do the dynamical load variation larger if not the ratio length/diameter is kept. That could be bad for the head gasket.

1) Yes we agree... The short/fine bolts (which are the same BTW as problematic Quad-4s) are definitely an issue... It was good that GM changed to longer coarser bolts... The new studs are even coarser still... As an aside most of the best dealers are "upgrading" blocks by using Normsert or Timesert kits for a 2004 and new block and switching to the newer longer bolts.

2) No, all LS xengines have 4 bolts per cylinder and all are deigned to work in temperature ranges that EXCEED the Northstar... The LSx engines have one difference... Coarse long bolts from day one.

3) Lots of speculation here... you have to "harden" aluminum parts that will be exposed to silicate (green) coolants... It is not clear if the year after they switched to Dex they stopped the "hardening" step... and then started again in 2000... Or if the longer bolts did the trick... we will never know

4/5) Agreed... Mine gets new dex every other year (and I check the coolant monthly)... but that doesn't explain why there is neglected DEX is in thousands of all aluminum LS1 and LS2 engines with basically no head gasket issues.

6) 97/98/99 Timeserted engines are starting to fail now for a second time... and the glue that is to prevent the serts from turning... doesn't. The serts are comming out of the block during the repair... This makes for extra problems and basically "finishes" the engine.

The "big end" of the studs is the same diameter as the time sert... so the clamping and the termal issues will be the same... just one less mechanical joint to fail.

2) Do they also have the Limp-home feature?

3) Yes, pure speculation. I think we can agree that something was changed in the manufacturing process in the years 97-99 and that the problem is gone now.

4/5) The same reason as in 2. Whatever that may be

6) They shouldn't. Unless the block is crystalized. This is from the Time-sert homepage.

TIME-SERT® is self locking. On installation the bottom internal threads of the insert are cold rolled to expand the mating external threads into the base material locking the insert in place. Locking mechanism is at the bottom of insert

If the serts comes out from the block despite their larger diameter the only possiblity is that the block itself is weakened (if the techs who installed the serts did their job right) and if the block are that weak it shouldn't provide more support for the studs either since the diameters are the same.

[Jan Olsson]

I never disagreed with the Guru, you couldn't he always had the facts. But I felt they should have cast in steel inserts into the block and said so.

Mike, I believe they ARE cast in.

I bet if the guru was still here he would be all over this product... In a good way... It is one of those... "I wish I had thought of this first"

I'm sure he would, but I don't think in a good way. I can recall him having a heated "discussion" about this very subject with a Cadillac Tech. Some of you may recall it. That said, he was a loyal GM employee and a staunch Northstar defender. I don't think he would have admitted a problem even if it where true and he knew it.

On the contrary I believe that he did admit that there was a problem, but he also said it had to do with the head gasket design/coolant system neglect and that owners of a 2004+ vehicle wouldn't encounter "problems" like that anymore. He seemed stubborn about some things but thats only because he had the knowledge about how things work from both a theoretical and a practical point of view. He had experienced a lot of engine toredowns and had also done a lot of Timeserting (with engine in place for that matter). Remember that he always said that he never had seen any head bolts come loose, nor any Timeserts.

I believe that he could have said that he had seen a few who failed in the above mentioned matter without scaring the crowd on the forums..

[KHE]

1) A head bolt is always experiencing a dynamical load. A long and small bolt is always better than a short big bolt from a dynamical load point of view. In this way they probably reduced the dynamical loads on the head gasket and prolonged the life of it. The coarser thread is probably to reduce the risk of real head bolts pulling due to a porous block.

2) A coarser thread can also withstand disassembly better than a finer one. There is also a question about how big maximum force is expected on the head bolts. The older LS1 engines had five bolts per cylinder right? The temperature creates an incredible load on the head bolts. The operating temperature on those could differ? Head gasket design etc. The Northstar engine has its “Limp-home” feature and to withstand the forces from the heat at 250+F the head bolts have to be highly strung to say the least. Perhaps the LS1 engine doesn’t have that feature?

I mean that a “low clamping force” joint doesn’t ruin the threads when dissembled. Think of all the other bolts on the Northstar engine. You never Timesert them, not even use Helicoils. Just because they aren’t highly strung.

3) You got me there J Some change in the casting process perhaps? That is of course not acceptable but they did fix it after they discovered it wouldn’t you agree? It takes some time before they see how changes work “in the field”

4 and 5) Coolant system service is your best bet to avoid head gasket failure. Not every one fails even if the coolant is never changed. Driving conditions like many cold starts and hard driving would accelerate thermal cycling on the gaskets.

6) Why problematic? The Timeserts if done properly are seated against the head. That and the threads hold them in place. The liquid thread locker is only to prevent turning of the inserts.

The bigger the diameter the less stress on the treads. If you have the same material you would expect failure on the inner thread before the outer one goes. Since the Timesert is made of steel that connection is stronger than the original one and since the Timesert has a much larger diameter than the original one it is also much stronger.

The studs are longer which is good. The larger diameter on the other hand could do the dynamical load variation larger if not the ratio length/diameter is kept. That could be bad for the head gasket.

6) 97/98/99 Timeserted engines are starting to fail now for a second time... and the glue that is to prevent the serts from turning... doesn't. The serts are comming out of the block during the repair... This makes for extra problems and basically "finishes" the engine.

The "big end" of the studs is the same diameter as the time sert... so the clamping and the termal issues will be the same... just one less mechanical joint to fail.

There is a mechanical swage that locks the timesert in place. That is accomplished when the installation tool bottoms out in the Timesert and then is driven through until the resistance is gone. The Loctite is a secondary if I recall properly. If a Timesert should fail, the block is not ruined - there is the Bigsert option which is an oversized Timesert. The Bigsert's original purpose was to salvage blocks ruined by the use of heilicoils.

[joeb]

i have seen 2 caddy's for sale recently with not completed head gasket jobs. a seville with the heads in the trunk and the other was a deville, not sure where the heads or block were.

[OynxSTS]

3) Yes, pure speculation. I think we can agree that something was changed in the manufacturing process in the years 97-99 and that the problem is gone now.

If only that were true... while failures in 2000-2003 blocks are rarer they are not nonexistent.

The 2004 - present N* seem to be bullet proof.. but even the "really bad" 97/98/99 usually took 80-100K to fail.

It is a shame that it took GM engineers over 10 years to recognize and then fix this car killer.