ARP head studs. Broken
 

I’ve got a 3.6 in my 83 SC.

I’ve owned the car for 6 years, I don’t drive it more than 2-3000 miles a year, had a valve adjustment right before I bought it...and mechanic gave it a thumbs up.

Owner prior to that did the 3.6 conversion. It’s been 10 years but at most 20,000 miles....both prior owners are Pelican guys.

The guy who did the swap sourced great parts, didn’t skimp in anything and he had the motor rebuilt by “one of the best guys around denver”...used ARP head bolts

On doing my valve adjustments, I found 2 nuts loose, and those two had broken head bolts.

I’m curious if this is a known thing with ARP (doubt it)...if it’s possible the “best” engine builder did something wrong.....or something else....

Anyone have some insight? I figure I can call ARP tech support just to see what they say, not expecting any freebies or warranty after all these years, just curious.

Do you have a pic of the ARP stud?

The 964 comes factory with 24 dilivar studs.
Just a thought....
Bruce

http://forums.pelicanparts.com/uploa...1615161833.jpg

http://forums.pelicanparts.com/uploa...1615161833.jpg

Is that head stud magnetic? If not it's probably the factory Dilavar. Easy to check.

Enamel coated Dilivar. 100%

Ok, "one of the best guys around" padded the bill... OR the seller was not forthright with you. That is not an ARP head stud.

As much as I like ARP head studs, and have used them extensively, we are going to give Henry's Supertech studs a go on our next builds that require more than factory steel studs.

As you need new ones, both of the above will work for you, do your research and make your choice.

Cheers

I have a set of factory Porsche steel head studs, I bought them new, cleaned them, taped off the threads, painted with VHT satin black brake caliper paint, then baked them at 200 deg for an hour. It's possible someone painted a set of ARP studs, but not likely.
Then I decided to just get the Super Tech head studs and remove one concern from my build.

ARP studs don’t come painted. The Dilavar studs would have had the rolled thread surface. Maybe ARP studs that were painted? All this “retorquing” bothers me. One wonders what torque they were using.

As stated above, it's NOT an ARP stud, nor is the nut correct ARP hardware. That's why I asked for a pic.

Something fishy went on. As Henry said, it's a Porsche dilivar stud, which are known to break.

Still has the factory nut..... and who would waste time painting an ARP stud... :cool::)

Its a factory original stud. Someone got lead down the garden path... so to speak...

Maybe they used ARP rod bolts on the build.......

The 964 used these, according to the PET:
Always possible that someone substituted the older style Dilavar. Easy to check with a magnet.
http://forums.pelicanparts.com/uploa...1615177971.jpg

Porsche says to use these now. But, when the 964 came out, there was no 993 part number head studs....much less the 993 Twin Turbo head studs.

Probably only US 964 engines... ROW seams to have 24 steel head studs, but I've only touched 3-4 3.6 engines.

Magnet doesn’t stick.

@speedy squirrel....I don’t understand the retorquing comment ...I don’t recall any other discussion, and on this motor, I didn’t ever torque the nuts, and I don’t have an invoice for anyone previously needing to torque the nuts.

Thanks for all the insight folks. I’ll look thru the build documents I have and see what I can find. Also, the original builder says he’ll talk to the engine builder Friday and report back. Seems like there’s more to this story.

http://forums.pelicanparts.com/uploa...1615207146.jpg

The stud in the OP pictures is definitely a coated Dilivar stud. I've seen hundreds.
All 964 engines came with a full array of coated, smooth shank, Dilivar studs.
It wasn't until the factory noted an unusually high failure rate of these Dilivar studs that they went back to steel studs in early 993 engines. This was very short lived. Warranty issues (weeping heads) caused them to reevaluate their choice of steel and reinvented the Dilivar. This time with an all thread monstrosity that offered a slightly more aggressive clamping force and marginally reduced failure rate.

ARP head studs have the bullet end to aid the nut being threaded on, so definently not ARP

Now you are just being ridiculous. The 993 Twin Turbo fully threaded Dilivar head studs work extremely well. It seems all you want to here is knock a part that threatens sales of your head studs.

Thanks Henry and everyone, good to know these aren't ARP.

So the consensus is these are factory 964 (circa 1989) head studs...breakage is normal, and I'm sure in time more will break. So I've got a project for next winter I suppose.

Thanks everyone.

Says the guy who never built a 911 engine.
It seems your accusations of nefarious intent says more about your character than mine. I don't need more sales.
I'm an engine builder not a stud manufacturer. I had the stud designed because nothing on the market fit our standards.
I hesitate to engage in these threads because my stud orders go through the roof and I can't handle the orders we already have. Even the mill is having a hard time supplying our material.
Right now we have back orders for all the material from the next shipment from the mill.

They are identical to the 12 Dilivar studs I just pulled from my stock '89 3.2L.

Says the guy who knows how to do research and who to talk to about things like this.

Your idea that only people who build engines have access to knowledge about head studs is stupid. It's also stupid of you to ignore the fact that guys with great reputations for building high performance Porsche air-cooled engines don't agree with you regarding the 993 Twin Turbo head studs.

Promote your head studs anyway you want and the forum allows. But stop bashing head studs that clearly work well and are used all the time by top level engine architects and builders.

on a race engine with around 30-40 hours, does one reuse the dilvar studs? or is it best to replace with a refresh?

If you're referring to GT3 race engines, they don't use Dilivar.
Porsche got smart and started using higher strength steel studs. Still the ridiculous all-thread but not Dilivar. I'm not sure if they life the studs or not. My guess is, no.

nope asking about the race engine that winders architect built.

Scott's recent posts on a number of threads definitely helped me decide to pull the trigger on my very first parts purchase for my short stroke build!



http://forums.pelicanparts.com/uploa...1615240333.png

Yea, I know... I've bought a few sets from henry over the years for all my builds... I was just trying to get a feel for winders thoughts on longevity. everyone has an opinion, but it seems that his is the only one that is correct.

My research suggests using them for the life of the engine. Obviously you want to inspect them at each rebuild but there is no reason I am aware of to replace them if they have not failed.

How many 400+ HP rebuilds can you get out of a 3.6L case?

Well scootergt3, if you had read my posts you will see that I have taken no position on Henry's studs. I have mentioned before that I had heard that Peter Dawe has used Henry's studs. That is certainly a positive thing for Henry's studs. William Knight has used them too. But not on his higher output builds.

My only point has been that the 993 Twin Turbo head studs are not the crap that Henry makes them out to be. They are used by most if not all of the big time high output engine builders. They are a viable option and the preferred option of many.

I am not trying to stop anyone from buying Henry's studs. I am try to stop Henry from bashing studs that clearly work well regardless of what he says. I am sure the SuperTec head studs will work great and that you will be quite happy with them. Why not? You have used them before.

My research led me down a different path. Is Henry's opinion the only right one here? I hope you would say no because of course it is not....

I am happy for you. I am sure they will work just great in your build.

Next thing we know, Scottie will be quoting Wikipedia
Once again, all you bring to the conversation is name calling and that "the cool kids use them"
This forum is where people who want answers about 911 engine rebuilds come to get the best information available for their project.
So no, I won't stop giving them the best information I have based on decades of experience. I will offer my opinion, offer the reasons for my conclusions and respond to questions both common (often wrong) knowledge and the somewhat obscure. I will continue to bring innovation to the table and thwart misconceptions and misinformation whenever it invades the conversation.

The 993 all thread is $1200 for 24 !!
Supertec is $725 and that includes nuts and washers.

I'm not an expert, but I have the Supertec in my two engines and they haven't broken like the diavar did they replaced or leaked as the steel ones did. They aren't 10.000rpm 1000+hp engines, just slightly hot modified street/track engines.
There might be other studs that perform equally well, but for 725 they are a bargain while the 993 are a rip off!
I would buy again if I build another engine.
Sorry for the endorsement Henry. ;)

http://forums.pelicanparts.com/911-engine-rebuilding-forum/1087450-cylinder-head-clamping-bore-distortion.html#post11245580

Nope. Just checked with Dawe and they use 993 Twin Turbo head studs on their high compression builds and Canyon head studs on everything else....

And what does this prove?
Not much.
If you check 100 different builders and you will get 100 different ways to build an engine. Most builders do tend to stick with what has worked for them in the past.

Except I am not finding 100 different choices in head studs for high output engines. The consensus amongst the top performance engine builders in the U.S. is to use the 993 Twin Turbo head studs for high performance builds.

What does it prove? It proves the 993 Twin Turbo head studs work and work well. If they didn’t work they wouldn’t use them. If they didn’t work, why would they use them and spend so much a crap product? Because they are all idiots? Not likely...

In the beginning there was a rock and a chisel.....all the experts used them to write.
Even God wrote on rock tablets.

Then came the pencil and paper.......OMG were all the chisel and rock guys idiots.....

Nope...they just used what they knew.

Ah, I see. They don’t know any better because they never keep an eye out for something better.

Except these are the builders that are still pushing the envelope and not just building the same old engines from 40 plus years ago.....

Innovation always precedes consensus.
I'm not saying they don't know anything, I'm saying you don't know anything and you don't speak for the consensus. You just parrot your own beliefs.