993 Head Studs
 

After asking and asking and asking everyone from local PCA members to local track road racers, I was repeatedly told to go to a local European Repair shop and ask for Phil, the shop's Porsche expert. So went there and asked for Phil. I told Phil that I was in the middle of a complete rebuild of my 1980 3.0L SC and I had several questions. Phil put down his tools and talked with me for about 45min. He answered ALL my questions and then gave me a long list of tip and tricks and even showed me examples on an engine he was working on (a great guy and endless base of knowledge).

Anyway, one of the things that he suggested and he had even put in his own 2.7L rebuild were, “Full Thread, Non-Magnetic, 993 Head Studs”. He said that he had used them on many engines (even race engines) and had yet to see a failure. He liked the expansion rate of these studs, especially with the Cold to Hot to Cold changes that we can see in late October/ early November, here in Michigan. He stressed, DO NOT use the Dilavar studs that were on the original exhaust side of my 3.0L (I had already planned not to).

Anyway, I went to the Pelican Part On-line Catalog and looked for these (suggested) studs. Guess what? The webpage (http://www.pelicanparts.com/catalog/shopcart/911L/POR_911L_ENGpis_pg7.htm#item31)
says this “Cylinder Head Stud, Mounted into case, (24 required, sold per each), 993 - fully threaded, DILAVAR, 911/911 Turbo (1965-98)” ……DILAVAR????? .....and at $$38.25 each ($918 for 24 set)
….he told me that these were less expensive than Raceware….?

Another question is that if Porsche knew that Dilavar studs had issues, why would the 993’s have them? Were the , “Full Thread, Non-Magnetic, Head Studs” used in production on the 993’s?

I am going to go back and ask Phil to clarify. However, are there different “Full Thread, Non-Magnetic, 993 Head Studs” than the ones on the Pelican page?



If anyone has info, please post.


http://forums.pelicanparts.com/uploa...1193346320.jpg
Broken (original) 1980 3.0L Stud

Thanks,

No they are the ones hes means, by non magnetic he is implying the diliver studs which are priced as above.

Be aware you 3.0 SC would only use 12 diliver studs on the bottom row the top 12 would be steel.

Steve

Are the Dilavar 993's different from the Dilavar's on my original 1980 911sc.

Anyway, I am replacing ALL 24 studs, NO MATTER WHAT!\\ ......What is a possible +200,000 mile rebuild worth?

Thanks,

At the expense of starting a war, there appears to be two minds regarding studs. One is to use steel studs, with varying choices including Raceware and Henry Schmidt's studs. Second is to use 993 Twin Turbo studs, which apparently are a better dilavar material.

I get confused personally, both sids of the argument appear to be valid in that there are very few stud failures with either of the two approaches. The more modern steel studs have lots of great experiences out there, but then again, the 993's did not have any stud breakage issues that I have heard of so they are obviously successful as well. I can see the value of steel (nice and strong), but then again, they are compressing what essentially is an aluminium column, so the dilavar's expansion rate, which is similar to aluminium, should maintain a more consistent clamping pressure.

I guess it comes down to price and preference?

All I know is that I have to buy a set for my 3.4 project car and I get slightly confused...

Dennis

use the supertec head studs. Call Henry to discuss. He is frequently on this board. He is in Fallbrook, CA. Google it to call if you want. That is my best suggestion and is also many here on the board.
Have any engine pics?? We love them...
Good luck!
Bob

There are lots of choices - Supertec's studs, ARPs, Racewares, Performance Developments (Neil Harvey), and a few others that I've seen online but never in person. I have had alot of customers use the ARPs and if those were not available, I usually source Neil's, albeit more expensive.

Anyone use the Porsche 993 twin turbo studs?

WOW! I got long winded and Dennis hit it right on the head. “Anyone use the Porsche 993 twin turbo studs?”

Furthermore, I need to THANK, ‘1972_911T (Steve)”… he is right…only 12 Dilavar on the exhaust side and 12 Steel on the intake side. Umm, I would think? …993’s are Dilavar and Steel. Right? Thanks Steve.

Anyway, I was once told “Brains Are Cheap” So, thanks to all of you for your posts (Brains) and keep it coming.

And if the choice wasn't hard enough now theres Casper labs high performance dilivar stud with life time guarantee :confused:

Decisions Decisions Decisions

Steve

For a 3.0 I'd just replace the lowers with steel 993 studs (not the dilivar ones). But I'm cheap. The steel 993 studs are the least expensive Porsche head stud.
-Chris

I did the same as Chris, Just the lowers with 993's

I used the full thread coated Dilivar studs in all 24 spots 7 years ago on my
2.7L.
All the nuts were still tight from the original torque. Can't ask for much better than that, I figure.

Thats ALL we use on 2.7's and larger, engines. :)

No ARP or Raceware studs for me, anymore.

Is there a reason for this? have you had bad effects from performance studs? A full set of the 993 ones works out $$$ compared to supertec et al.
Steve

Oh yes,...:)

We've had issues ranging from loose head nuts to loss of head sealing between the top and bottom row of studs from excessive clamping when very hot.

Porsche REALLY put a lot of engineering into the Dilavars and the late 993TT ones are bulletproof. Head torque and clamping stays uniform from cold to hot (even on Turbo motors that can see 450 deg head temps).

Dennis,

I was at Hima Haher's shop in Calgary a few years ago. He was more than happy to show me the work they were performing on his 911 Turbo race car. He suggested the 993 (turbo?) studs as well. He's a wealth of knowledge and I wouldn't hesitate to stop buy and pick his brain re: any other engine rebuild questions.

http://www.riegeltuning.com/index.cfm

Tim K

Good info.

Dilavar in all 24 spots...and 7 years to boot :). Steve Weiner seems to agree. It sounds like a bit of a hit in the pocketbook, but broken studs were the reason I start this project.

Even though I am enjoying the rebuild, I would rather be driving. So if I can get 7 years of driving and not rebuilds, than that sounds good to me.

Steve, would you still use dilivar studs on a cylinder where the heads studs are not encapsulated and exposed?

I sure would, especially with alloy cylinders,..:)

I assume you're talking about a T-4 application here.
I'd be interested in Steve's answer to this also.

Steve do you have any knowledge or opinion on the casper labs delivar studs that have recently been listed in the pelican catalogue?

Steve

I have no experience with them.

Given whats at stake and my potential liability for the customer, I will stick with the factory ones since they have been quite successful. :)

I would only try them on a shop engine for a few years before we risk them on a customer's engine.

No, I meant like a stock 930 or 964/993 cylinder where the stud bosses are cast in and inbetween the fins are closed off to keep the cooling air from reaching the studs, versus earlier cylinders where the studs are exposed to the cooling air.

I have had customers use the dilivar 911 studs on the 356 with our cylinders, but I was curious about how the elements might affect the dilivar or promote the hydrogen imbrittlement problem.

I would have no grief on the use of late Dilavars in all of them with the exception of Biral cylinders since I don't think they need them.

I see no issues with Dilavars on the 356 and have never experienced a failure due to hydrogen embrittlement,...... :)

Good to know. Can you post the part numbers for the correct dilivar studs then, for posterity's sake so when someone is searching threads they can find the right stud?

The part # is lost in time for me, but here's a pic. These were the latest & greatest at the time.http://forums.pelicanparts.com/uploa...1193447148.jpg

Here you go:

993.101.170.51 (These are used on the TT, RS, and RSR engines)

These are the studs I selected and installed on my rebuild. If they're good enough for 993 TT with over 500HP, that's good enough for me. :D
After over 6K miles and 2 1/2 years of use, no problems whatsoever.

I used the 993 Dilavar studs in the lower row in my SC rebuild last winter.

My philosophy was following : I have heard that some of the very high tensile race studs, needs re-torque ? - i do not want this at all ! second, i heard that these studs could come lose because of the thermal expansion of the engine.
third, why would Porsche continue with the Dilavar technology, if they was so bad ??

What is the worst thing - a lose head stud or a broken one ...and what
will maybe appear first ??

Some pictures :)

http://forums.pelicanparts.com/uploa...1193688902.jpg


http://forums.pelicanparts.com/uploa...1193688954.jpg


http://forums.pelicanparts.com/uploa...1193689045.jpg

I am just jumping on this thread. My stock 1991 965 is about to get all new studs as one was broken when they went in to see the cause of some leaks at the valve covers. Would you folks suggest they use these (or other) factory Dilivars? Also, the car has almost 60K miles. Should I have them do valves and guides while they are in there? I don't want to do more than I need. Hell, the car seemed to run fine and only went in for a suspected bad alternator. :(

Did you see this month's (Dec) Excellence mag about BA's comments on head studs (page 46)? :

When I rebuilt my engine over two years ago, I contacted Hendrick Porsche and ordered a full set of 993TT head studs. The studs I received were the full threaded type described by BA above.

The full treaded type is the 993 TT original Porsche, using Dilavar material.
Even if they are Dilavar they must not be compared to the old studs used from .... 1975( i beleive) and also used in my 1978 Turbo which had 18 out of 24 studs broken after long term storage.

If you ask RUF or any other major european professional engine tuner what they use you will find that they most probably use the full treaded original 993TT studs and not aftermarket studs. There is a reason for this.

I am using the 993TT studs for my rebuild even if it by far is the most expensive option.

so, what is the conclusion on the "new" currently available 993TT studs:
1 are they steel or dilavar?
2. is there a space in the middle of the stud, as BA said, that is NOT threaded?
3. are they epoxy/or something coated?
4. should the readers here use this stud for ALL rebuilds or just the turbo rebuilds?
5. IF 2 different studs recommended, what stud for which applications? (one for turbo the other for all other applications?)
***HOPEFULLY THE EXPERTS CAN CHIME IN TO SET THIS SUBJECT TO REST...if that is possible***
Bob

Studs for your 911
 

Hi,

You can replace your studs with the standard studs that the factory began using in 1984 ( 3,2l engine ), they are cheap and they do not fail like the ones on the 3,0l engine.

The 993,101,170,51 is very nice but they are expensive, I have bought 24 of them for my 3,0l race engine but I believe that the 3,2l studs would have done the job as good as the "993" studs.

I will go for the 3,2l studs next time.

Regards/ P.R

Supertec head studs are the only head studs that are designed with modern engineering concepts.
The Supertec stud offers more threads at the case end (the deeper into the case you go the better the structural integrity) highest quality SS and hardware that is superior to anything Porsche offers for this purpose. The head nut are 12 point, serrated flange, fine thread for positive grip and smoother, more accurate torquing. The washers are hardened and ground.
This 12 point nut also offers the clearance necessary for twin plug conversions.
We also offer a life time warranty. They will never break, you have my word on it.
The best thing is that they are offered directly for our host.

http://forums.pelicanparts.com/uploa...1197042313.jpg

Hi Henry, can you comment on 2 items and how your product addresses these please:
1. possible "loosening nut" concerns requiring re torqueing at future intervals
2. thermal expansion concerns of the rod material... how does your metal compare to dilivar, 993TT material what ever it is and plain oid steel studs.
To me, the real issue here is 2 fold: #1 what is the application as maybe 2 products are needed i.e. turbo an NA (heat expansion rate...) #2 some applications only need a basic? rod HOWEVER, ALL RODS NEED PROPER CLAMPING FORCE SO NUT DOES NOT LOOSTEN AND THE METAL OF STUD IS INTERRELATED TO THIS.
Can you possibly make this an easier topic to understand? (maybe heat is the dividing line i.e. turbo & NA engines??)
Thanks as always...I enjoy learning for you and all on this board!!!!!!
Bob

The serrated flange and fine thread both address the loosening issue. Proper torque and a stable platform are necessary for continuous cylinder to head sealing.

As for thermal expansion, you're on your own. I am not an engineer so when we wanted to produce a superior stud we hired a fastener engineer to address the issue. He selected the material based on heat, cylinder materials (of course there was a compromise because of differing cylinder materials) and exposure issues as stated by me and my 30 years of Porsche engine building experience.

Just so we're clear about the purpose of the delivar stud. Porsche was trying to prevent head seepage on cool down that lead to warranty oil leak issues. The stud is not intended to create a stable or even tight seal under operating temperatures.
The CE ring head the same purpose. Hence it's eventual removal then replacement in later big bore engines.

Although some people will have problems with a product and not contact the manufacturer, this is generally not the case in the Porsche world. That said, no one ( not one customer) has contacted me with any complaints about this product. No loose studs, no cylinder sealing issues and or course no failures.

This product is the seventh in a line of development studs and at present we are sold out because we can't keep them on the shelf. Road race teams, import drag , high performance turbo and street DIY customers all enjoy reliable service from these stud kits.

Henry,
Thank you for your continued contributions to the forum. Are you saying the reason for oil seepage from the head/cylinder area was corrected in large bore (greater than 97mm (?)) with the addition of CE rings or other material?