ARP headstudd issue in 996T

[BoxxerSix]

I realize this forum is 99% aircooled relative, however I trust the information from the techs here more than anywhere else so it's fitting. Besides, the bottom end of this motor is essentially the same as yours.

I'm in the process of building an M96.70 for an '01 Turbo and have run into a major issue with ARP head studs. This is not my first build by far, but is the first time using this stud kit in one of these motors. The studs are an undercut shank with ~1" of thread on one end and about .5" of thread on the other with a bull-nose end. Normally a stud with a bull nose in a blind hole application would have the bull nose end go INTO the register and bottom out on the hole(like EVOMS or Supertechs), thus locking the stud in place against further rotation(IE when torquing the head) and providing a positive stop setting all the heights evenly)

Installing the studs in this fashion causes the studs to come up short once the coolant jacket/gaskets/head are all in place. With an ARP washer and nut fully seated and torqued to ~15ftlbs, the nut does not get full thread engagement(~4.5 out of 7 threads in the nut). Moreso, doing it this way puts only about 1/2" of total stud thread into the case which certainly cannot be enough to support the tension load without pulling threads down the road(hence why I only did a light torque of 15ftlbs now for checking).

So I called ARP and talked to "a tech", who told me the bull nose goes out. Also told me thread length of 1.5 times the stud diameter is sufficient.........that's for cast iron/steel!!!! Not a soft metal like aluminum. I asked what the free lengths were for this stud(7.625") to verify that they were the correct studs. After some other misc discussion that didn't help he directed me towards the factory for more answers, which led to messages and no return calls.

Going by the ARP specifications for installation, I flipped the studs and checked again. This time it was worse. By the time I got the nut started on the end of the thread there was less that 1.5 threads of engagement in the nut. On the flip side there was more thread in the case now. Whoop-de-do.

IF, I were to back the studs out of the case so that I just retain the full 1" of thread into the case(no bottom out in the register) I could likely get full engagement, but now there is nothing to keep the studs from rotating when threading on the nuts let alone when torquing them down. It's as though they NEED to be threadlocked into place at a set height like OE studs, which is highly unorthodox for an aftermarket stud like this.


I've never used ARP's headstud hardware on any aircooled motors either, so I have no basis for this to go off of. Has anyone here who has used ARP hardware in an aircooled build run into an issue like this? ARP itself has been useless to say the least in trying to sort this out with me and at this point I refuse to put these studs in this motor. ~$850 worth of studs that don't work the way they should IMO.....


For what it's worth case is original, never been split.



Some pictures of the stud installed according to ARP's specs shown with and without the washer/nut in place, and in comparison to stock stud at install height(ARP stud bottomed in register)










I guess I'm just looking for some input from the techs. I have zero information in regards to factory specs on stud register depths and thread depths for this case

Now if the customer had only purchased EVOMS studs like I told him to I likely wouldn't be posting here now, but he cheaped out to save himself $600. That savings he thought he had just went out the window!! Henry, I know you don't work on water pumpers but how about making a nice set of 7.625" long 10mm supertechs with a bull nose to them huh

[304065]

What is the installed stud height (your equivalent of 135mm on an aircooled engine)

How much engagement do you have with the studs set to that height?

If the answer is, "not enough" then the studs should go back to ARP as a defective design.

[Targa Time]

I used ARP head studs in my build also. As with you I didn't find the "tech support" too helpful. Head stud length on the 3.0 is critical and I would assume the same for the 996 engine. +1 on what 304065 wrote. But keep in mind the studs may not be bottomed in the case to achieve the proper measurement. On the air cooled engines they are held in position with Permatex Red. Find the stud length measurement and measure from the case to the top thread, not the bullnose. The bullnose is just there to center the nut and prevent cross-thread.

[BoxxerSix]

You do not threadlock the ARP studs into the case. You CAN do it, but it's an unnecessary step and one that must be done under the clock to get the studs torqued before the thread locker sets up(about 20 minutes at 65F). Even if that was the case, there is absolutely no way to maintain any sore of accuracy in a set stud height when spinning on the nuts or torquing them down. The studs simply spin into the case further no matter what you do they are THAT loose in the threads.

Apparently I'm not the first to have come across this in the 996 world and many have lost motors due to these studs rattling loose and/or pulling threads form the case. The threads are also apparently rolled incorrectly on this stud causing very poor thread contact in the case, which explains why the studs would rattle up and down 2-3mm in the holes when not bottomed out.

Mind you OE studs still fit in the thread bores just fine. They just cannot cope with the pressure levels and the HG's leak. Car was @ about 1.5bar on twin Tial Alpha A28 billet turbos and made 599.89 AWHP last dyno session before it started bending rods.

Regardless at this point they're not being used. Made some calls and spoke with Ian @ Evo MS and purchased the last set of their headstuds they had in stock. Pricey @ $1400 + shipping, but they're holding with zero failure in most of the 800+WHP 996 builds and with zero install issues.

Now I just have to get a refund from ARP for these poorly designed studs i cannot use

[BoxxerSix]

Just an FYI, not that it really matter much here I guess.

I spoke with numerous people who have had their motors fail due to the use of these studs in their builds. A majority of them were due to the studs coming loose because of the poor thread contact in the case, some pulled the case threads.

I've also noticed that many of the distributors that used to sell this kit have since pulled it from their stock and are no longer selling it, including the distributor that this kit was purchased from.

Again, likely makes little difference for the aircooled motors of this forum but is food for thought none the less. I will personally never use ARP headstuds ever again in another Porsche build, regardless if their other 4206 kit is fine or not. Raceware or Supertec from now on.

[304065]

It will be interesting to see how ARP deals with this issue.

It's a small market for $1400 headstud sets out there, but if ARP wants to be in the market they need a competitive product. I would call them and explain all the issues in the most matter-of-fact way possible and pose the entire thing to them in the form of a suggestion as to how they might improve their product.

If they refund your money and their tech people are genuinely thoughtful that is the best outcome. If on the other hand they try to give you a hard time. . . .in Manhattan we have an old saying "you can shear a sheep many times but you can only skin him once."

[BoxxerSix]

I have yet to contact ARP about the return of these studs yet, but I wanted to post some side by side comparison pictures of the ARP studs and the EVOMS studs showing the definitive length issue at hand here.

Side by side comparison, with the case end threads lined up to each other on the left side. Evo stud on top. Note the substantial increase in case thread on the Evo stud, as well as the bull nose that goes INTO the case to provide a dead stop for the stud at the bottom of the stud register in the case




Close up of the nut end thread of the two studs as aligned above(case threads at equal depths). Evo stud is to the left, and the "bull nose" on the top of the Evo stud actually contains a shallow hex cavity for installation/removal of the stud.



Side by side comparison of the two studs as they would sit bottomed in the case register. That's how these type of studs are supposed to be installed, not locktighted and set to a specific height like OEM studs are.




And now a close up of the nut end thread of the studs as aligned above(to register bottom). The lack of available thread is plainly visible in this photo





With these pictures I cannot see how ARP can have a foothold in saying they were designed properly for the application, and not accept the return. Time will tell when I place the call/emails tomorrow.



Huge thanks to Ian @ EVOMS for holding the last set of studs they had in stock for my customer until he bought them

[Henry Schmidt]

I guess it's time for Supertec to build a stud for the water cooled world.
Yikes, did I really say that?

[996tt_Stevo]

I would chat to Todd at Protomotive Protomotive - Welcome to the Worlds Fastest Porsche Tuner

[BoxxerSix]

Definitely a market for them Henry. Make a competitive 10mm headstud kit for the 996T and they would sell. $1400 for these + OEM headnuts(~$4.75 each), these junk ARP's are ~$550-$700 for the set with nuts/washers.

[Henry Schmidt]

Supertec is now offering the 996T replacement head stud.
All the quality of the original Supertec Head studs with the addition dimensions required on the water cooled engines.

Pricing is competitive and they should soon be available through our host.

[MBruns]

Looks like the A 1 tech studs, they work well, we have seen many head lifting issues with the current ARP studs for the TT's,

Mike Bruns JBRacing.com

[BoxxerSix]

About ****** time Henry A little late for this build but I will certainly be using them in future builds thank you!

FWIW......ARP basically told me to jump off a cliff more or less. Last time I'll be using their product in a Porsche that's for sure.

[Spenny_b]

Have to say, I spoke to ARP's "technical" team on Monday...Jesus, I know I'm from the UK, and have an English accent, but I might as well have been speaking Russian.

The guy just didn't know anything, all I was asking was for confirmation on head stud and rod bolt part numbers for my M30/69 3.3T rebuild (their listing only goes up to the 1989 3.3T...I'm sure they're the same but I've not stripped it down far enough to measure and identify)

Was very disappointed with level of knowledge from the manufacturer....will be considering RaceWare or SuperTec (the only reason I started with ARP is that I have their rod bolts in my Se7en engine).

[BoxxerSix]

Get the supertecs and never look back.