Have heard two diff. opinions on replacement studs for 3.2L. Which is better and why, Dilivar or titanium or is there a difference?

 

Hi:

I've never heard of titanium being used on these air-cooled engines due to differences in expansion rates and the inability to maintain cylinder head torque.

I use the latest Factory Dilivars used in 993's as the best for head retention and maintaining even torque over the whole range of engine temps. These newest Dilivars do not suffer the corrosion and breakage that the old ones did.

Even since I had a set of heads loosen up during a race weekend using aftermarket studs, I try to stick with the Factory items in these particular cases.

 

Steve,

 

Steve,
Thanks for the reply. This was mentioned to me by someone who had the studs replaced on their 88 3.2L and their mechanic insisted on titanium over the dilivars..... this was about 4 1/2 years ago. He had it in for a valve adjustment and one broken stud was found so they did the job on them all using titanium. I'm considering purchasing this car and it now has about 60K, job done with about 50K miles. Should I be concerned about the diff. expansion rates? Is this a deal stopper? All else sounds good with solid maint. records, etc..

 

Hi:

I've never used aftermarket titanium studs in anything over the past 28+ years including RSR-934-935 engines and a 917/10.

I really have no experience with them, good or bad. I do know that titanium expands at different rates than the aluminum alloys used in Porsche motors and would be a bit hesitant about using them, given the proven success with the Factory steel and latest Dilivar studs.

 

The current factory studs, a 993 part number, are steel, and have been used for a number of years. I wonder if your friend used Raceware, or similiar stud, which are made with an alloy.

 

Didn't they use titanium in the 6 million dollar man ?

 

No, absolutely not, you're thinking of the Bionic Woman ..........

 

I just did the studs in my 88. And what I recommend is the use of the latest 993 micro encapsulated studs. Some call them dilavar, because they are listed as such. But if they are dilavar or not, who knows. They certainly look a hell of a lot different than the old black studs that corroded and broke. They will have the proper expansion rate. To be honest, I know nothing of titanium studs. I didn't even know they existed for the 911.

 

I would imagine that they are not really titanium studs. The wrench was probably told that they were a space age material and he assumed titanium. If the paperwork is good, check the part numbers on the invoices from the repair.

Here is the deal on Titanium: Thermal expansion of Ti (B 120VCA) is 5.2x10-6 in/in-F and AL (6061-T6 wrought not cast) is 13.5x10-6 in/in-F. Steel has matches the expansion closer than titanium, it maybe too stable for this application (although much stronger than steel).

 

Titanium is very "notch sensitive" so it is prone to cracking when used as a fastener. The normal surface scratches from torquing in addition to the stress risers formed by the threads make it extremely difficult to use as a fastener. I can't imagine it being used as a stud as the accepted procedure is to dispose of them after using them once. The only place where they are used are airplanes and spacecraft.

Are you sure the studs weren't made of Unobtainium? So much of the parts made for these cars seem to double in price when they are made for a Porsche.

Wayne

 

They probably are not titanium at all. Most likely they're Raceware or ARP, both of which are alloy. I used Raceware in my own engine. I've never heard of one breaking. I'd stay away from Dilivar.

 

Part number for the replaced studs is RTE-1022 HSK. Anyone recognize ?

 

Raceware: You can get them from Pelican Parts for $562.50/set

RACEWARE Cylinder Head Stud Kit (sold as a complete set, Studs Only), 911/911 Turbo/964/993 2.4/2.7/3.0/3.2/3.3/3.6L engines

 

Thanks Tim! You solved the mystery for me. The PO still swears he got titanium and saw the box thay came in.... well if it made him feel better, no harm. Thought I was getting a bionic car though.