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

[sammyg2]

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

[john walker's workshop]

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.

[sushinav]

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.

[Gene-o]

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.

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.

[Gene-o]

Originally posted by john walker's workshop
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.

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.

[KobaltBlau]

yes, some of the studs have an epoxy coating.

[88911coupe]

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

[anthony]

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.

[chrisp]

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).

[KTL]

Originally posted by clarelaw
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.

Nine? 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.

[Rick Lee]

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.

[KobaltBlau]

Originally posted by Rick Lee
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?

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.

[bigrubberjeep]

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.

[KTL]

Originally posted by bigrubberjeep
..................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.

[KobaltBlau]

Originally posted by KTL
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.

['78 SC]

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.

[strother]

Originally posted by '78 SC
...The only warning came when #3 doubled up and the head started rocking and made the telltale exhaust noise we all learn to fear. ...

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.

[john walker's workshop]

gargle and flap your lips at the same time.

[Wil Ferch]

John.....

Perfect !!!!

- - Wil

['78 SC]

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.