Yet another Dilivar head stud question

[vytenis]

I have Wayne's book and have read a number of posts regarding "the ticking time bomb" of Dilivar head studs. I have an '87 911 with Dilivar lowers.

Quoting Wayne from his parts catalog "As the displacement of the 911 engine increased over the years, the increased stress caused by differing thermal rates of expansion often caused the head studs to break or separate from their mount in the case. This often resulted in a leak between the piston and the head. Porsche decided to solve the problem by using Dilavar studs. However, there were reports of these studs breaking under pressure prematurely. There are a few good solutions. You can replace your studs with the standard Dilavar studs that the factory began using in 1984. Or you can use high-strength aftermarket studs."

I've read that they keep making the Dilivar studs better and better. I'm doing a top end rebuild at 100K miles (and while I'm in there) and don't want to cut any corners. Nor do I want to drain my bank account unneccesarily.

So are Dilivar studs after 1984 OK for use on a stock engine configuration?

"V"

[Steve@Rennsport]

Originally Posted by vytenis

So are Dilivar studs after 1984 OK for use on a stock engine configuration?

"V"

IMHO, yes indeed, provided you use the late 993TT ones.

[tom1394racing]

The Dilivar studs used on the 3.2 Carrera and later models were the coated type.

I have not seen the corrosion related failures on these that are common with the lower Dilivar studs on the SC motors.

Comments??

[Jesse16]

I have a similar question regarding the Dilivar head studs. I've got the engine out of my 87 Carrera for a top end job and some leak management. All the head studs seem fine to me. Car has 187k miles and this is the first engine apart work ever. Car has always lived the rust free life so the question is, any grave consequence to just leave well enough alone! Not hard to convince me to just leave em for now and make a quick check at each valve adjust going forward. Hate fixing stuff that isn't broken.

[Carrerax]

you can also just use the same steel studs as the top row and be fine. They are availailable here at PP or I know Tom1394racing will sell you used ones for very inexpensive. They are not known to break.

[brads911sc]

Dump them, 993TT or otherwise and use Supertech. Half the price and better product...

Originally Posted by vytenis

I have Wayne's book and have read a number of posts regarding "the ticking time bomb" of Dilivar head studs. I have an '87 911 with Dilivar lowers.

Quoting Wayne from his parts catalog "As the displacement of the 911 engine increased over the years, the increased stress caused by differing thermal rates of expansion often caused the head studs to break or separate from their mount in the case. This often resulted in a leak between the piston and the head. Porsche decided to solve the problem by using Dilavar studs. However, there were reports of these studs breaking under pressure prematurely. There are a few good solutions. You can replace your studs with the standard Dilavar studs that the factory began using in 1984. Or you can use high-strength aftermarket studs."

I've read that they keep making the Dilivar studs better and better. I'm doing a top end rebuild at 100K miles (and while I'm in there) and don't want to cut any corners. Nor do I want to drain my bank account unneccesarily.

So are Dilivar studs after 1984 OK for use on a stock engine configuration?

"V"

[vytenis]

The Porsche engineers used Dilivar on the bottom for a reason. I know that the ARP, Raceware, Supertech headstuds work, but it is overkill ($) for me. Going to go with the new Dilivar bottom studs.

[brads911sc]

Overkill ($)? the Supertec is $610 for 24 the Dilivar is $1128 for 24 with washers/nuts... Supertec come with a lifetime warranty. Dilivar does not. Dilivars have failed. Supertec have not. Seems to me you have it backwards ($)... I wouldnt put Head Studs in the list of briliant porsche engineering successes... Im just sayin...

Originally Posted by vytenis

The Porsche engineers used Dilivar on the bottom for a reason. I know that the ARP, Raceware, Supertech headstuds work, but it is overkill ($) for me. Going to go with the new Dilivar bottom studs.

[tom1394racing]

On a stock motor, a good set of used steel studs for the bottoms will be just fine.

[Flat6pac]

On street use, I never have had to apologize for failure. When the 993 dilivars were a buck more that the stock dilivars I would install them but now I wont even retorque dilivars, Ive woke up the next morning with nuts and stud pieces on the floor.
Bruce

[Flieger]

Bruce, you use steel, then? What if the customer is willing to pay the money for the 993 studs or whatever is best. What do you use then?

[roy gray]

just use steel.the germans continue to reinvent the wheel unsuccessfully while the japanese perfect their original designs and put out a superior product.a 911 motor,especially a street motor doesn't need dilavar ever.or
"aviation"grade.just use steel.

[ALEX P]

Headstuds seem to be a real achilles heel on all 911's particularly SC's but now that 3.2's and 964's are all getting past 20+ years IMO they are going to cause more and more issues in the later cars.

I went through a similar decision for my rebuild and the choice came down to using the 993TT studs (the fully threaded ones), Supertec or Racewear ones. 993TT and Racewear ones were ruled out due to OTT price and I bought the Supertec ones. Seem to get good reviews from everyone who have used them, best priced and you can't argue with a lifetime warranty.

[ChrisBennet]

Originally Posted by tom1394racing

The Dilivar studs used on the 3.2 Carrera and later models were the coated type.

I have not seen the corrosion related failures on these that are common with the lower Dilivar studs on the SC motors.

Comments??

As a data point, I replaced a broken lower head stud on a friends 3.2 a few years ago so it does happen. I agree that it probably isn't very common.
-Chris

[Henry Schmidt]

The best choice for every aircooled Porsche engine is Supertec studs.
You don't need them just like you don't need a Porsche to drive to the store. You can just get in your Yugo and trundle on down the road.

[lindy 911]

vytenis,

I would never recomend this but since you have made up your mind to use dilivar I'll save you the purchase price of new ones and send you the ones I got from Porsche brand new for free. I have all the new studs for the bottom except one. You'll have to buy that one because when I installed these brand new studs in a '78 SC, not an hour went by until I heard a "PING" and one of the studs turned into a projectile.

FWIW, I have Supertec studs now and they are far superior to what Porsche did, overkill or not. Send me a PM with your address and I'll send you the studs.

Lindy

[IDGAF27]

Originally Posted by lindy 911

vytenis,

I would never recomend this but since you have made up your mind to use dilivar I'll save you the purchase price of new ones and send you the ones I got from Porsche brand new for free. I have all the new studs for the bottom except one. You'll have to buy that one because when I installed these brand new studs in a '78 SC, not an hour went by until I heard a "PING" and one of the studs turned into a projectile.

FWIW, I have Supertec studs now and they are far superior to what Porsche did, overkill or not. Send me a PM with your address and I'll send you the studs.

Lindy

+100. WOW, that speeks for it self.

Vytenis imk kas geriau. remontuoti antra karta brangiau, negu padaryti teisingai is pradziu..........

[vytenis]

Aciu

Cogitating!

"V"

[shrtshck]

For what it is worth, I just replaced the Dilivars on mine with the standard steel ones. As with you I have a 87 with 100k miles, none of the Dilivars were broken but it is good insurance based on the experience of others. I'm happy to say that all the Dilivars came out without issue, 5 to 10 minutes with a propane torch and they came free.

[vytenis]

Originally Posted by lindy 911

vytenis,

I would never recomend this but since you have made up your mind to use dilivar I'll save you the purchase price of new ones and send you the ones I got from Porsche brand new for free. I have all the new studs for the bottom except one. You'll have to buy that one because when I installed these brand new studs in a '78 SC, not an hour went by until I heard a "PING" and one of the studs turned into a projectile.

FWIW, I have Supertec studs now and they are far superior to what Porsche did, overkill or not. Send me a PM with your address and I'll send you the studs.

Lindy

I'll bite. PM Sent. I am going to fixture in a jig to test bolt preload and will share results here. Might snap some. While I am not a "boltologist", I did design bolted joints in a previous life. I have a little time in my rebuild before I'm ready for head studs.

"V"