Head studs -- 911 or 993 or aftermarket

[dduclaux]

To all -- I have read and reread Wayne's Rebuild Book, particularly Chapter 4 on head studs and I have a question regarding the 993 Dilivar head studs vs. the original earlier Dilivar head studs.

Is part #993 101 170 51, described as 993 Dilivar head studs an upgrade to the early Dilivar head studs that let me down after my last rebuild?

Please help me understand these issues.

Thank you very much in advance,
Duane Duclaux
'79 911SC

[Superman]

Your 3-liter case is stronger than the magnesium cases. so, the head stud pulling problem does not apply to your engine. So, the fancy Dilivar studs that Porsche used to address the pulling problem are not needed on your engine. And finally:

Factory steel studs, like the ones on your intake side, are just a tad over $10 each. You can pay more than that, to purchase more Dilivar studs, which as we all know have a habit of breaking, so as to address a problem your engine does not have. Or you can pay less, for studs that do not have a history of breaking.

[jgparker]

The 993 steel stud is exactly $8.65 at Pelican, and is a very good way to go IMHO. Part number is 99310117202. Please do a search for "head stud" on this board, the subject has been beaten to death recently.

Good luck,

JP

[Superman]

Okay, well at $9 I'm not going to throw rocks at the 993 Dilivar things. I've heard they're more reliable now, and it took the old ones twenty years to snap.

[Doug Zielke]

I still have 11 'used' Dilavars if ya want to try 'em.....

[echrisconnor]

That's almost half the price of the steel 911 ones:

Steel Cylinder Head Stud, Mounted into case, (24 required, sold per each), 911/911 Turbo (1974-89)
C-101-172-00
$16.75 (EACH)

[ischmitz]

The 993 101 170 51 dilavar studs are the ones used in the 993TT. I went with those for my 964 rebuild.

My understanding is that the regular 993 uses steel studs and the 993 TT uses the dilavar version. They are all threaded except a very small section in the center. Some say they look like cheapo hardware store fasteners or that the threaded area has more stress risers or cuts into the cylinders. Oh well, at least I haven't heard of broken or pulled studs on 3.6 TT's And what is good for a 993TT should do O.K. for my motor.

One of the reasons the earlier dilavar broke was that there was apparently a bad batch and they corroded. My original 964 dilavar studs where coated and did not show any corrosion. They were fine but I still swapped them for the peace of mind.

Aftermarket studs are a nice alternative if you are willing to spend the extra money but seem overkill IMHO.

Ingo

[Wayne 962]

There is much debate on this subject. Steve Weiner likes the newer studs, Bruce Anderson doesn't. I recommend the early steel ones as they don't seem to have any downsides to their use.

-Wayne