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

Gene-o · 02-10-2005, 12:26 PM

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.

Rick Lee · Rick Lee's Garage

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.

livi · 02-10-2005, 01:04 PM

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

KobaltBlau · 02-10-2005, 01:06 PM

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

emcon5 · emcon5's Garage

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

Bill Verburg · Bill Verburg's Garage

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

Tim Hancock · 02-10-2005, 01:25 PM

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.

sammyg2 · 02-10-2005, 01:35 PM

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

clarelaw · 02-10-2005, 02:12 PM

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.

Gene-o · 02-10-2005, 02:28 PM

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.

KobaltBlau · 02-10-2005, 02:32 PM

Quote:

Originally posted by clarelaw
I would guess with the SC if the dilivar studs are not broken yet, they will be soon.

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.

Quote:

Originally posted by Gene-o
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?

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.

Walko · Walko's Garage

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

Superman · 02-10-2005, 03:27 PM

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.

livi · 02-10-2005, 03:29 PM

What Michael said!

Markus

chuckw951 · 02-10-2005, 03:29 PM

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

KobaltBlau · 02-10-2005, 03:47 PM

Quote:

Originally posted by Superman
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.

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

GettinHeadStuds · 05:00 PM

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

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

anthony · 02-10-2005, 05:14 PM

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.

imcarthur · imcarthur's Garage

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

Driver Ed · Driver Ed's Garage

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.