Another victim to a broken head stud

[NaFe]

Well that got a little bit off topic quickly, lol.

I'd be interested to know what stud type people have replaced their headstuds with. If a new set of standard headstuds are going to last 200,000kms then i dare say I will either not own the engine or something else would have gone wrong before then that may drive me to replace studs as precaution.

I just checked on UK site i'm familiar with ordering from and standard steel stud is 7GBP vs. the 27GBP for divalar... times that by 24 and there's a BIG difference.

[tazzieman]

Buy the best you can afford. Probably won't affect resale price.

[NaFe]

Buy the best you can afford. Probably won't affect resale price.

Thats assuming the "better" are directly proportional to the added cost.  With standard steel SC studs being 1/4 of the cost of the divalar studs, I question if they last 4 times as long or are 4 times better.  That's why I asked what others have replaced theirs with, for a bit of first hand experience

 

Cheers, Nath

[Harvs11]

Well that got a little bit off topic quickly, lol.

I'd be interested to know what stud type people have replaced their headstuds with. If a new set of standard headstuds are going to last 200,000kms then i dare say I will either not own the engine or something else would have gone wrong before then that may drive me to replace studs as precaution.

I just checked on UK site i'm familiar with ordering from and standard steel stud is 7GBP vs. the 27GBP for divalar... times that by 24 and there's a BIG difference.

I used steel inlet side head studs to replace the broken Dilivar studs.  My reasoning against new 993 Dilivar studs was this.   Unlike earlier 2.7 magnesium cases the SC has an aluminium case so the risk of pulling the thread is reduced. My particular engine isn't pulling big HP so the stresses aren't a big factor.  I wasn't doing anything to increase performance, just getting back to a usable street engine. Working to a budget, so cost was also a factor.  Doing the work myself I managed to keep the expense to a marriage saving figure. 

I've done 40k since the new studs went in, including track days where the rev limiter was in play.  Still going strong. 

 

[MFX]

Was it pig-headed engineers or bean-counter accountants that continued with the Dilavar development when they should have rethought the issue? I bet these were the same guys that OKed the IMS 'solution' in the Boxster & 996.

Porsche is still building engines with issues and then just using band aid fixes. The 991.1 GT3 is a prime example. Those engines have a major issue with the hydraulic finger followers not getting oil. They then wear out themselves and the cams. Heaps of GT3's have already had to go back under warranty and all Porsche has done to fix it, is to use a better hardening treatment on the cams and finger followers. This is just going to delay the problem (probably just long enough to get out of warranty), it hasn't actually fixed the issue. I believe the 991.2 has addressed this issue, but I am not sure that it is compatible with the .1 ....

[Zelrik911]

I used steel inlet side head studs to replace the broken Dilivar studs.  My reasoning against new 993 Dilivar studs was this.   Unlike earlier 2.7 magnesium cases the SC has an aluminium case so the risk of pulling the thread is reduced. My particular engine isn't pulling big HP so the stresses aren't a big factor.  I wasn't doing anything to increase performance, just getting back to a usable street engine. Working to a budget, so cost was also a factor.  Doing the work myself I managed to keep the expense to a marriage saving figure. 

I've done 40k since the new studs went in, including track days where the rev limiter was in play.  Still going strong. 

 

This is good advice for NaFe.

Has anyone heard of the 'cheap' replacement studs breaking after installation?

this is another piece of good advice " keep the expense to a marriage saving figure" . Can I add that you should never keep all your receipts in one place or do a spreadsheet of costs - I guarantee your wife will find it!

 

[tazzieman]

Thats assuming the "better" are directly proportional to the added cost.  With standard steel SC studs being 1/4 of the cost of the divalar studs, I question if they last 4 times as long or are 4 times better.

If only cost was directly proportional to "quality", life would be easy! Is a $50 Porsche oil filter 5x as "good" as an $8 one?

For mine , if I was doing a full rebuild I go best quality , if just buttoning up after a broken stud or two I'd use the steel ones. Unless I planned on keeping the car forever.

[Peter M]

Has anyone heard of the 'cheap' replacement studs breaking after installation?

Zel,

If you are asking about replacement steel studs made by "OEM suppliers" the answer is no I haven't.

[Coastr]

How many SCs are going to do another 100 or 200 km on top of what they already have?  How many are going to be all-weather hot/cold cycles that the original studs were exposed to?  For most cars the days of daily driving are behind them.  It takes a lot of driving to put 100k on a car.

[Peter M]

 

...standard steel stud is 7GBP vs. the 27GBP for divalar... times that by 24 and there's a BIG difference.

Nate,

I don't think we have answered your question successfully yet, so I'll have a go.

My understanding is that SC's have steel top studs and dilivar bottoms, like my 3.2.

If you are doing a rebuild, the common practice is to replace the dilivars with new steels and leave the original steel top studs alone.  (Assuming they aren't damaged or corroded of course.)  Therefore you only need to replace 12 and not 24.

If you are only doing a repair to replace the broken one(s) only, the practice appears to be just use a steel replacement.

However the difficulty is that to remove only one is a big job and before you know it it becomes essentially a top end rebuild.

I was hoping Bruce would weigh in with his advice but it is clearly temping to just ignore the one broken stud for now and just see how it goes.

[NaFe]

Thanks Peter,

I have come to the decision that I will be replacing the broken headstud for sure - rather than run the ticking time bomb of other potential issues that may arise as a result.  

I also have historically had a lower compression ratio on no.2 which has always played on my mind and looking underneath I have developed a few more oil leaks than I previously had.  This may be as a result of not looking for a while (the vehicle has recently come over from the UK having been in storage for 4yrs).  I must fess up, the SC engine is in fact in fitted to my 1972 Vw Kombi.  There are a few other bits and pieces that are persuading me to remove the engine, like fitting a larger fuel tank in the kombi as well as fitting a cam sync for a future megasquirt efi upgrade.  Dreams of fully sequential CoP setup would be nice etc.

I am also of the thought that if I am going to replace the bottom studs, then I may as well replace to top - even if they are less susceptable to breaking, they are 25yrs old and would have been subjected to similar heat cycles albeit on the inlet side.

Based on what the engine is fitted to and the unlikely chances of of it being destined for the track, my thinking is to run the standard steel studs all round.

[Buchanan Automotive]

With a 2.0L , 2.2L,2.4L,2.7L , 3.0L 911SC or a 3.2 or even a 964 , when dismantling the first thing is to discard all 24 head studs , to leave the top row in place is madness and asking for a breakage later , remember , thin head studs of this nature are extremely thin in regards to just about all other car engines out there & like any bolt ( they are a type of bolt ) they have a natural stretch in the first torquing sequence decades before & with thousands & thousands of heat cycles decades later they are on their last legs

Be it head studs or bolts ( same sort of thing ) they all lose their ability to do their job in old age & with the top row being just steel they are the cheapest "part" you can install inside the engine "individually speaking " 

Remember also , what holds the the 6 individual barrels & the cylinder heads to the crankcase ?
Answer }  The thin head studs

What holds the weight of the cam boxes & camshafts( these are heavy ) + 12 rockers & 12 rocker shafts & the 12 valves & valve springs ( sitting out in the breeze "Horizontally" ?
Answer } The thin head studs

What holds ( fights back ) against the strain of the timing chains ?
Answer } the thin head studs

What holds the weight of the exhaust manifolds ( heat exchangers ) under the engine bolted to the small exhaust studs in the heads ?
Answer } the Thin head studs

What takes the strain of the expansion of the alloy engine components ( alloy expands quite a bit ) & the contraction as the engine cools down ?
Answer } The thin head studs

What takes all the outwards / massive combustion impulses from the firing of each cylinder , millions & millions & millions of times ?
Answer } The thin head studs

I am amazed they last more than two or three heat cycles or even a day for that matter 

For the later versions to last as well as they do is remarkable

But ALWAYS replace all 24 head studs on dismantle , now its up to you "IF" you choose to do the bottom row with the correct head studs( 3.0L>) or not 

Subject Closed

Regards
Bruce Buchanan  

Buchanan Automotive

[Peter M]

LOL!  Tell us what you really think Bruce, don't hold back!

[tazzieman]

LOL!  Tell us what you really think Bruce, don't hold back!

Do it right and do it once is what my father would say. You get what you pay for is what my father in law would say. 
Buy an old 911 and make sure you have a secret chest with $10k in used notes is what I would say. 

[Peter M]

Actually at about $10USD each they have to be cheapest 911 engine part going.  What's another dozen in the scheme of things!

[ANF]

Actually at about $10USD each they have to be cheapest 911 engine part going.  What's another dozen in the scheme of things!

It's amazing how quickly a series of these "cheap" parts can add up to a few thousand before you know it!! but hey it's all fun and games......

[MFX]

It's amazing how quickly a series of these "cheap" parts can add up to a few thousand before you know it!! but hey it's all fun and games......

I can't agree more with that statement. A full rebuild (even keeping everything stock) adds up very quickly in 'cheap' parts alone.

[bumble]

What Bruce said.

Most common choices for after market are ARP, RaceWare, SuperTec (Henry Schmidt) and A1.  Any of these will do the job.

A big problem (as Bruce hinted) but underestimated is corrosion caused by their exposure to a very hostile environment.

Religious wars have been fought over this issue!

[NaFe]

I used steel inlet side head studs to replace the broken Dilivar studs.  My reasoning against new 993 Dilivar studs was this.   Unlike earlier 2.7 magnesium cases the SC has an aluminium case so the risk of pulling the thread is reduced. My particular engine isn't pulling big HP so the stresses aren't a big factor.  I wasn't doing anything to increase performance, just getting back to a usable street engine. Working to a budget, so cost was also a factor.  Doing the work myself I managed to keep the expense to a marriage saving figure. 

I've done 40k since the new studs went in, including track days where the rev limiter was in play.  Still going strong. 

 

Just read in Wayne Dempsey's H"ow to rebuild and Modify..." book that he would also recommend replacing the Divalar studs with the steel top studs also.  He obviously talks about Raceware etc and some other aftermarket, but if that's what he's recommending then I'm happy with that.

First time a cheap option has been the recommended route

[Harvs11]

Just read in Wayne Dempsey's H"ow to rebuild and Modify..." book that he would also recommend replacing the Divalar studs with the steel top studs also.  He obviously talks about Raceware etc and some other aftermarket, but if that's what he's recommending then I'm happy with that.

First time a cheap option has been the recommended route

Cheap is relative.  Even if you are going to use the less expensive steel studs it's worth sourcing correct Porsche OEM parts.  Bruce's advice is spot on...new bolts,nuts,washers everywhere is essential, failure of a re-used part is going to get expensive.