3.0 ARP head studs w/undercut threads?

[1979911sc]

I am looking at installing some new ARP head studs in a 3.0 sc motor and wanted to see if anyone knows if I need to be using the undercut stud version? I have found ARP head studs that I want to use but I am not sure if they are the right ones for my application. They have a kit ARP Part #: 204-4206 I know they come with 12 point nuts but looks like there might be a couple of different styles including an undercut version or maybe they just come this way? Anyone use these or know which ones to us? Thanks Troy

[1979911sc]

Anybody use these? trying to figure out if they are all stainless too?

[Turbo_pro]

I don't know if there are different ARP head studs but in the last four 911/930 I've had built I selected the Supertec studs. After reading horror stories about ARP studs coming loose and Dilavar studs breaking expectantly, the Supertec stud with it's life time warranty and highly developed design, seems like a no-brainer.

[EBS_Don]

Yes, the 204-4206 is correct for all air cooled 911 type engines through the 993. They are made from ARP's L19 stainless material. There no "options" on this kit and they all come with the same nuts and washers.

[sjf911]

Is there a better option for securing them in the case than red loctite?

[1979911sc]

Thanks Don that is what I needed to know. Was looking at ARP because they seem to have a good reputation and price. I have heard the supertecs are good but not sure if they are a necessity on a mild rebuild. If I had some what appear to be good used steel studs to use would you advise against using them on a mild motor and just go new?

[chris_seven]

Originally Posted by EBS_Don

They are made from ARP's L19 stainless material

I thought L19 was similar to H11, which is best described as a Hot Work Tool Steel.

If this is correct then it is typically a 5% Chromium steel and is about 0.35% Carbon. It air hardens readily as it has about 1,5% Molybdenum.

It should not really be described as a Stainless Steel.

It does have excellent strength and reasonably good fracture toughness BUT it is known to be sensitive to Stress Corrosion Cracking, particularly when there are chlorides in the environment. (Salted Roads?)

I must say that unless this material was quite well protected from corrosion, and it is also sensitive to hydrogen embrittlement when Cadmium plated, I would hesitate to use it for the lower studs on a 911 motor.

ARP state the following:

L19: This is a premium steel that is processed to deliver superior strength and fatigue properties. L19 is a very high strength material compared to 8740 and ARP2000 and is capable of delivering a clamp load at 260,000 psi. It is primarily used in short track and drag racing applications where inertia loads exceed the clamping capability of ARP2000. Like most high strength, quench and temper steels – L19 requires special care during manufacturing to avoid hydrogen embrittlement. This material is easily contaminated and subject to stress corrosion. It must be kept well-oiled and not exposed to moisture.

[1979911sc]

Interesting
Just wanted to confirm some sites I have found ARP 204-4206 say:
Fastener Style Stud
Head Style 12-point
Fastener Material 8740 chromemoly
Fastener Finish Black oxide
Washers Included Yes
Cut to Fit No
Quantity Sold as a kit.
Notes Fits 911 and 930 turbo models. "Dilivar style" replacement

Is it just the studs that are stainless?

[nick_911]

I used the arp studs recently.
I've used arp studs in motors with triple the amount of power than my 81 sc rebuild and never had issues before.
I ordered the exact same kit and no the washers and nuts are not stainless. Not sure what material but they were both black.
I got two extra nuts and was short two washers in my delivery and they sent the extra washers out right away so even their service is pretty good.
For the price and my application I didn't think twice paying $485.00 for the set.
Nice packaging too.
Cheers
Nick

[1979911sc]

Nick, So what you are saying is that the studs are stainless or polished and just hardware is not right?

[nick_911]

Yes that is correct.
I'll post a pic later on of the kit when I'm in front of my pc.

[Targa Time]

I'll save you the effort Nick_911.

[chris_seven]

Originally Posted by 1979911sc

Nick, So what you are saying is that the studs are stainless or polished and just hardware is not right?

Guys,

AISI 8740 isn't a Stainless Steel either it is a 0.4% Carbon Chrome/Molybdenum Steel similar to AISI 4340 but stronger.

If you want Stainless Steel fasteners Supertec studs are most likley the best option around.

The standard OEM studs which can be bought with a resin coating are also quite cost effective.

[pharlap71]

when I was stud replacing I was going with ARP, but no one had them, ARP said 3-4 weeks. With further research decided on SUPERTEC, absolutely no regrets, top quality product and the customer service (Henry Schmidt) equally superb. Also I have built high compression engines even air cooled diesels that have tremendous loads on the fasteners, a 911 is a different animal, it is not just about strength and clamp loads. The factory steel ones are incredibly strong but they do "ping" off, and sometime engine cold and not running, and when you look at the fracture it is a fresh, clean break.

[mcclusk]

I am aware of many arguments for and against loctite at the case end. ARP just says use the grease at both ends, and a number of techs I know suggest running the studs in dry at the case or with a bit of loctite 271. What do you think? Thanks.