How common are head stud failures in SC's and 3.2's?
 

Hi gang,

Still collecting information here. One of the things that has me concerned is dreaded head stud failure. It's my understanding that they could break at any time. How common are these failures? I'm getting the impression they occur quite often, especially in low mileage cars. Are head studs more likely to fail in an SC or a 3.2? Enlighten me please.
Thanks for your input,
Gene DiGennaro
Baltimore,Md.

You're asking for a lot of nightmare stories here. I checked the headstuds before I bought my SC in Nov. and they were fine. 2 mos. later two were broken. My car has 93k miles on it. Studs break more from time than miles. If I were doing it again, I probably would not buy an SC that had not already had the studs replaced. It happens on 3.2's too, but then valve guides on those are likely to go before the head studs.

Hi Gene-o,

I can really appreciate Your worries !

I spent 6 months collecting information. Read thousands of threads on different forums, my bookcase is spilling over with books, magazines etc.

Amongst others I covered the topic You mention in the futile hope of an answer that could be aplied mathematically to my equation eventually leading to a figure that gave me answer to what exact modell year I should decide on.
No matter how much information I gathered, I would not feel certain.

I DID get the general feeling that whether going for the Carrera or SC, they both have their issues BUT with a proper PPI they are both equally fantastic cars.

Finally, I went for a Carrera and I am ABSOLUTLY THRILLED !

Good luck hunting !

Markus
Carrera 85

Gene,

The consensus seems to be that the head studs breaking comes from time, specifically surface corrosion making them more vulnerable. 3.2s have not had as many problems, but many people (including myself) believe that they will be similar to SCs after a few more years (then the SCs will be older, but you get the idea).

if you have a shop check the head studs during a PPI, they will have to pull the cam covers off, and they will probably charge you an additional 100-200 bucks. The seller also may not be keen on this since it _might_ introduce oil leaks that aren't already there. on the other hand, the shop could fix an oil leak at the same time if there is already one from a cam cover.

I still think it's a relatively small fraction of the SC population that is encountering broken studs, but of course it is no fun if you are one of the population. The only solace is that a top end rebuild is not really all that expensive compared to other items on the car, though it probably seems exorbitant now. For example, you might need a transmission rebuild or a clutch replacement, both of which are pretty expensive if you don't do them yourself, and you can't necessarily detect if one of those things will happen in the next year or two when you buy the car.

In other words, these cars are very reliable but you have to take the chance that something major might happen, and hold some cash in reserve just in case. But remember how much your buddy with the new car is losing in depriciation, and be happy :)

SC and 3.2 Carrera head studs have the same part number.

As the 3.2s age, you are going to hear about more of them with broken studs.

Tom

Even 964s have ben popping up w/ broken studs lately

The bottom studs are typically what break on the SC's as they were divilar, the tops studs were steel and they do not seem to be a problem. The Dilivars over time seem to get spots of corrosion which cause stress risers or weak points for a crack to start. Some argue that Divilars are best when rebuilding, but I think most people replace the lower Divilars with steel when they rebuild and I have never heard of any problems since (assuming a basically stock non turbo engine). New Divilars would probably last a long time though before corrosion weakens them again.

My SC lower Divilars were all intact until I removed them for a rebuild at which time one broke during removal. Looking at it, it probably would of broke eventually with enough expansion contraction cycles. I replaced all the lowers with steel and I feel confident that the engine will last a long time now.

Here's a scientific survey:
How many 911SCs do I own? One.

How many head studs broke on it before I changed them to steel? One.

Hope this helps ;)

When I bought my 81 SC all the head studs were fine. Two years later I had nine broken on the bottom. All the tops were fine. Needless to say, I ended up doing a rebuild because of broken studs. I replaced all of my studs with ARP raceware studs. I would guess with the SC if the dilivar studs are not broken yet, they will be soon.

I really do appreciate all the help, thanks. I'm looking to buy in about one year's time. Assuming I find the right car, and a PPI indicates the studs are good, should I nip this problem right in the bud and replace them right away?

Thanks again for your thoughts and inputs,

Gene DiGennaro
Baltimore,Md.

Perhaps, but it depends on the car's life. If it has been in a dry climate, garaged, and not driven in wet weather, you have a much better chance of longevity than the opposite situation.

I say no, just check them when the 15k valve adjustment rolls around, and if they're good don't worry. It's not like 1 or 2 studs being broken (assuming they are not on the same cylinder) causes sudden or catastrophic damage.

I would think that the type of driving teh car sees will be just as dependant as the weather as to the studs breaking.

If you only use you car every other sunday and only for a short trip then the motor may get up to operating temp but the stud and all the bits further out may not and any moisture / corrosion will be compounded. If on the other hand you are using your car as a daiily driver and clocking up fifty or six miles each way every day then the studs will probably last a lot longer.

All of my 911's have been daily drivers and teh only time I have had problems with them is when I have got a new toy and stopped driving them daily.

IMHO drive the car hard every day and you should have no problems.

Michael

Buy an SC that has had a head stud transplant. And if the head studs have been replaced, then the top end should have also been rebuilt. So, rebuilt engine. With 98mm P&C's. And race buckets. And stiffer torsion bars. and.......

If I were to buy my first 911 right now, knowing what I know, I would look to pay $16 -18 K for someone's already-sorted track car. Or upgraded street car. It would have relatively fresh bushings, refreshed tranny, refreshed engine, etc. It would have 8" or 9" rear wheels with 7" fronts. That kind of thing. It'd save me lots of money to do that.

What Michael said!

Markus

I've owned 2 911SC motors. Both needed to have the head studs (bottom row) refreshed at some point.

Of course the work all has to be done right.... Maybe I'm obsessive-compulsive.

Heh... uh... ya... this is part of what inspired me to change my login name...

http://forums.pelicanparts.com/uploa...1108086333.jpg

Oh and... I believe it a question of when rather than if...

Gene, I just bought an SC. The car checked out fine so I went with it. All these cars are a risk. I think that whatever your budget is you need an extra $3-4K as an emergency fund just in case.

My advice is to buy for the long term. It would be bad luck if one needed to spend $4K on an upper end right after you bought the car but at least after that you know you're good for another 100-150K miles on that engine. Over 10 years that only $400/year.

FWIW, I've heard just as many stories of SCs going 250K miles without a rebuild as I've heard broken head stud stories.

I did a lot of research on this when I was shopping in 2003 - 04.

Heat, humidity & a lot of sitting around appear to accelerate breakage. If the oil is not sloshing around, heat & humidity corrode the studs & snap . . .

In 1984, Porsche started using painted dilivar studs which appears to retard, but not eliminate, the problem.

Ian

One additional data point: My '82 SC had two broken head studs (both on the bottom) and I had 'em replaced when I had the engine rebuilt. I agree with others who have said that it doesn't make sense to preemptively change the studs. If you do regular valve adjustments, you can't go too long with a broken stud without knowing about it.

BTW, I know this belongs in the classified section but I have 11 1/2 used dilavar studs for sale. Any takers? ;)

the black painted dilivars are much less likely to break, so far. maybe that's because they're newer. the surface of the untreated ones, like the one pictured, etch with rust in the area between the head and cylinder, and the exposed area at the cylinder base, then they break. you can see the penetration of the rust in the broken end. 83 and later usually have the painted studs. i've become less concerned with those over the years.

I have been told many cars run fine even with a few broken studs. It doesn't have to mean instant rebuild unless it is causing running issues.

That's pretty much the route I'm thinking. I think I'd rather look for a car that has a rebuild already done rather than a garage queen. Of course, alot depends on the quality of the rebuild though.

By painted, do you mean an epoxy coating? That would go a long way to retard corrosion. This is a field I am rather interested in as I work in materials engineering. I was even thinking that a Titanium Nitride coating like the kind seen on drill bits would be quite corrosion resistant, but I'm not sure if the coating ( since it is a ceramic) would be able to expand and contract with the stud as it thermal cycles.



Thanks again for the thoughts and opinions crew.

yes, some of the studs have an epoxy coating.

I seem to recall this issue can be solved by using the fully threaded 993 bolts. I guess this does not really answer the question of SC's and Carrera's tendency to have broken head studs in the first place. I guess though I'm asking is it a good idea to use the 993 studs in the event you're faced with replacing them?
TIA

People usually put the upper steel studs in the lower position. Even new dilivar studs should be good for another 20-25 years if you are doing a rebuild.

I bought my car knowing that I would rebuild the engine at some point. Whether it was a missed shift or a broken head stud I knew what I was up against and bought the car accordingly.

I agree with anthony, if you buy with this stuff in mind it's a much more enjoyable experience.

I also agree with superman that buying someone else's project is the way to go. This assumes that the stuff that was done, was done well. You can save money here. I don't know if there are well sorted SC track cars in the $16k-$18k range though.

For me it was best to start with a solid baseline and end up at 2.5 times initial purchase price. Everything has been touched/upgraded to a spec similar to the competitive PCA stock class cars (except for the tranny).

Nine? :eek: I'd venture to say that at some time somebody re-torqued those lower studs, and over-torqued them? I'm no expert by any means, but I don't recall hearing of nine broken ones! Wow. BTW, ARP and Raceware are two different manufacturers of head studs. Not trying to be a jerky. Just helping others avoid misinformation.

I agree with buying a well sorted car if that's you're desire. At the same time, you can buy a much cheaper car that needs some work. Then you learn things along the way. I can't believe Super would do it any differently if he had it to do all over again. I recall Jim learned a lot (and made alot of good friends) doing his rebuild?

I, on the other hand, would/will definitely do it differently the next time around. My car was a low mile car that demanded a pretty decent selling price. I still dumped a bunch of $ into it to "fix it up." Next time i'll buy a solid-bodied, tired car for a low price and save myself alot of $ up front on the initial cost.

Like the others said, the head studs are sorta like rolling the dice. You just don't know. Even a PPI doesn't guarantee you'll avoid the issue. Rick's SC is a perfect example. And some shops are starting to turn down PPI's these days, since so many people like placing the blame on somebody else nowadays. Meaning, the buyer will claim that the shop's PPI should have detected the issue. All brands of cars have their quirks. One of Porsche's happens to be the head studs.

This also makes me wonder what I would have done, had I broken a stud while doing my own PPI at the owner's house. What happens when you break a stud while lightly torquing it and you don't own the car yet? Also, JW, my lower studs were not painted black and I have one of the very last SC's made. I even have a Carrera case with no sump plate. My lower studs would not stick to a magnet either, so I'm pretty sure they were Dilivar. Car sure pulled like a champ and did not smoke before the rebuild. But the stuff we found once she was apart was pretty appalling.

You broke it - you buy it?

I like do do my own work, but I think there are some drawbacks to doing your own PPI.

My car had 101K miles on it when I tapped the valves, when we took the engine apart everything was in perfect condition (minus 3 valves slighly bent and small marks on the top of the pistons. I decided to go with new OEM studs since the last sent had lasted 20 years but I did upgrade the rod bolts to ARP and the valve springs hoping to avoid future money shifts.

Good call on the rod bolts. Valve springs are good if the motor's going beyond 7K. That said, even the best hardware in the universe won't save the motor when you grab the wrong gear at high engine speed! :(

I agree on the PPI issue. You break it,.......... But in the same sense, you could argue that the shop doing a PPI for you would have done the same thing? Tough call.

To me it makes sense to have the shop do the PPI anyway, because if they say "xxxx needs to be replaced" there's some negotiating power there. if you say the same thing, and I were the owner, I'd say "well, that's just your opinion and you're trying to get a good deal"

Just MHO.

Another data point regarding the miles v. years discussion...

During a valve adjust two years ago I discovered my 78 SC with only 31k had 5 (actually 4.5) broken studs. The only warning came when #3 doubled up and the head started rocking and made the telltale exhaust noise we all learn to fear. The other breaks were scattered over three different cylinders and not noticeable (at least not until we removed the lower valve covers and it started raining hardware).

IMHO there's a certain inevitability to this. Don't think buying a low mileage vehicle will allow you to dodge the bullet.

I'm a 911 newbie. What's this sound that I should be fearing? I'd hate to have a head stud break and drive around like that, probably further screwing up my engine.

gargle and flap your lips at the same time.

John.....

Perfect !!!!

- - Wil

Strother,

A cylinder with 3 of 4 studs intact is still pretty well tied down. When 2 exhaust studs are broken, the head can rock slightly, since its only support on the lower side is the cam tower. The sound is a "phtt phtt" kind of thing, similar to the sound American iron makes when an exhaust manifold is cracked. You will not hear it at idle, but when accelerating along side a wall you can hear it echoing off the wall.

At first, I thought I had a leaky manifold gasket and made a note to check it when I did the next valve adjust. Ignoring can be costly. The bouncing around damages the head sealing surface and requires resurfacing. AMHIK.:(

Try a few searches. There is a wealth of info here about this.