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Discussion Starter · #1 ·
First post here so hello. Have spent lots of hours reading here on mod stuff. I have an 04' i'm building up from what is now a bare shell that was a fully running car a year ago. In parts acquiring mode. One thing has led to another and what was going to be a simple engine refresh turned into a ground up build aiming for around 1000whp on a blower setup.

I have a set of ARP2000 head studs going into a Teksid. Recommended torque for these i believe was 85-90ft/lb but i've seen many use 100 which i plan to do as well.

Given we are always on a quest for better clamping forces as power and boost increase, has anyone here ever tapped their block for 1/2in "race" studs in order to get an additional 20-30ft/lb on the heads? I've been told be reputable engine builders that its "not needed" which I agree with, but this just curious if anyone's done it on a street/strip car.

Thanks.
 

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1965 Superformance 427 Cobra, & 2022 BMW M850
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ARP's current TQ spec for the studs is 85 ft/lbs. Originally it was 100 ft/lbs. Why the difference? Original studs used a washer that was smooth on both sides. Proper assembly calls for the washer to be dry and have use ARP lube (highly recommended) used only on the bottom face of the nut to mitigate friction between the nut and the washer during torquing. Few builders ever read the instructions that far or practiced the careful application of the lube, hence the 100 ft/lb spec at that time — according to ARP. For those of us who did we found 85 to 90 ft/lbs to be more than adequate.

ARP2000 studs purchased today use a different washer. The underside of the washer is serrated. ARP wants you to place this side of the washer against the head and apply ARP lube to the threads and the underside of the nut. The serrations make the accidental application to the underside of the washer a non issue now — according to ARP.. The Torque spec for the current generation ARP 2000 stud kits is 85 ft/lbs.

I have always assembled heads to the engine with dry washers. I apply ARP lube to the stud threads and the underside of the 12 point nut. I have never used the six point nuts so I have no experience with them using this technique. I recommend the 12 point nuts, they have a very nicely shaped and positioned load bearing face called a nut collar. ARP typically ships a mid sized 12 point nut with the studs. Although 11mm fasteners in general are rare ARP does use 11mm fastener technology on the coarse threaded block side of the stud. The fine threaded top side of the stud, where the nut attaches, used 7/16 NF threading on the studs I last used.

To understand ARP nut metrics the following diagram will help;
175672


The numbers reference the following metrics;

➊ Diameter / Thread pitch in threads peer inch. i.e. 7/16 x 20
➋ Nut Head Height
➌ Nut Collar Diameter
➍ Socket Size

I don't recall the standard 12 point nut provided with the ARP 2000 stud kit. It is a midrange size that, if I remember correctly, will look like their part number 300-8303 in the chart below.

175674


My preferred 12 point nut part number is either 300-8374 or 300-8314 which are larger all around and provide a better clamping experience. ARP will not supply these in the kit so you will be in for some additional expense to obtain them.

The two best ways to minimize your cost of acquisition is to either buy the kit with the hex head nuts and throw away all the hex head nuts replacing them with the more robust 12 pt nuts or just buy 20 individual studs through Summit or Jegs and then buy 20 bigger #8314 or #8374 12 point nuts, don't forget to get washers if you go this route.

Using the right hardware and ARP lube, 85 ft/lbs and no more than 90 ft/lbs will do the job very nicely w/o putting the block at risk. At somewhere right around 110 ft/lbs you will break a brand new NEMAK / Aluminator block. This is a good experiment not to conduct.


Ed
 

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Discussion Starter · #3 ·
Thanks Ed for that awesome info. I never knew about the larger nuts i'll take a close look at those.

The kit I have is the 2000 series w/12pt nuts, part # ARP-256-4201. These are 7/16 studs as you pointed out (11mm), and your advice not to exceed 90 ft/lb on these is well taken.

My question more pertains to drilling out the block to accept larger 9/16 studs (I was incorrect mentioning 1/2in in my original post) or 14.3mm. By using a much larger stud, it would allow for a much higher clamping force of 120-130 ft/lb.

Just to clarify, are you stating that ANYthing over 100 ft/lb on an aluminum block would be dangerous, even if using this larger stud?

Thanks.
 

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My understanding was you can't go nuts on the torque with aluminum blocks because it'll crack the block. At least that's what was said when I saw a few blocks cracked around the deck after making some power.
 

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It is not the torque that breaks the block it is the tensile preload, more on that in a bit. The 9/16" studs have a ½" shank and a ½ x 20 NF top thread. The studs are used as service studs for blocks that have damaged the stud anchoring thread(s) in the block. The studs are a $700 fix for a problem on a $600 Aluminator block or a $400 Teksid block and that price does not include the cost to install the studs!

The reason the anchor end is 9/16" instead of ½" is the major diameter on an 11mm x 1.5 thread is 10.98 mm or 0.43". The pitch diameter on a ½ x 13 NC coarse thread is 0.45" which means you only have 0.010" of aluminum per side in the hole to anchor a ½" stud. You would immediately pull the stud out of the block casting before you got to 20 ft/lbs of torque. That forces you to a 9/16 NC thread for the anchor point in the block.

The upper portion of the 9/16" stud uses a ½" shank and a ½ x 20 NF thread that ARP recommends a torque spec of 125 ft/lbs for. The important consideration is the clamping load or as the engineers refer to it, the preload on the stud. At ARP's recommended TQ spec for a ½ x 20 fastener the stud will have a preload of 18,500 lbs of clamping force.

Your ARP 2000 studs at 90 ft lbs of torque will have a preload of 15,000 lbs of clamp force. When you go to 100 ft/lbs of torque you are over 20,000 lbs of preload. Somewhere between 100 ft/lbs of torque and 110 ft/lbs of torque on the 11mm ARP 2000 studs, the block will crack. This is what it looks like when it does;


175675


The crack goes through the water jacket on both sides of the fastener. This block is unrepairable. The 9/16" stud is a race block only repair. Look at how thin the casting is at the bottom of the stud anchor point. It gets thinner when you go to a 9/16" thread. The 9/16" repair studs are good for race blocks with a lot of machine work and money in them that you are trying to sneak through the end of a season or so. They are not a good fix for other blocks and I would not recommend them.

The difference between a 15,000 and 18,000 lb preload, while not insignificant is not the cause of your head gasket sealing problem, if you are having head gasket sealing issues. You should be looking elsewhere not at 9/16" head studs. Your engine should seal up perfectly at 85 to 90 ft/lbs maximum on ARP's 2000 studs. Do not forget to retorque the heads after the first warm up.

The old saying about if it is not broke ... definitely applies here. These are exceptional engines that produce stunning power for their displacement. Follow the cook book, don't try to out science the 25 year old recipes for building the engine and you will be happy, BTW so will your engine and wallet.


Ed
 

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Discussion Starter · #6 ·
That answers my question then and was my primary reason for asking it…..upgrades are always a compromise and my main concern was block integrity with the larger stud. Ill stick with the tried and true 2000’s and stock bore. Thanks again. And yes i do plan to re-torque the heads a couple times during the break in process. Much apprec.
 

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That answers my question then and was my primary reason for asking it…..upgrades are always a compromise and my main concern was block integrity with the larger stud. Ill stick with the tried and true 2000’s and stock bore. Thanks again. And yes i do plan to re-torque the heads a couple times during the break in process. Much apprec.
Retorquing is a good discipline to embrace but, in general, a single retorque is all that is required.

When we start a brand new engine with aluminum heads and block there is a considerable growth in the block deck height and the thickness of the cylinder head once the engine reaches operating temperature. On an MLS gasket this produces a very substantial increase in crush on the head gasket reducing the gasket "stack" height from the assembled dimensions just after the build was completed but not yet started.

As the engine cools the new stack height of the now further compressed MLS gasket remains at its new thinner dimension. The thinner dimension reduces the tensile loading on the studs because of the thinner gasket and encourages gasket failures particularly on supercharged engines.

The obvious but not so easy fix, on our engines, is to re-torque the heads after the engine returns to ambient temperatures. When you do, the next time you start the engine it will not further compress the gasket which means (mercifully) that we do not gain anything from second or third retorques.


Ed
 

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I went with the hex nut version of the ARP 2000 head stud kit and I think it will be good enough to reliably hold 30+ psi of boost on my 2001 Teksid block.
175679


By the way, Accufab has a nice video on head studs and they mention that most cylinder head gasket problems are caused by an improper tune up (too much timing).
Accufab Head Stud Tech
 
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I always torque to 100 ft/lbs with ARP 2000 studs on my teksid blocks. 1600whp, 35+psi boost. I also never 're-torque'. Not claiming what I do is better or best, just stating what I do and what provides success for me. I do everything I can to mitigate head gasket issues because having to change them is a major PITA, engine has to come out.
 
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100 ft/lbs as been the long standing ARP recommended TQ spec for their 2000 steel studs, washers and nuts that you and I use,Tony. Today, ARP claims that the same studs but using their new washers that are serrated on the head side and not on the nut side should only be torqued to 85 ft/lbs.

When I called to inquire about the difference and the reason, there was no logic to their answers although the answers were consistent no matter who you talked to.. It basically boils down to do it because we changed washers and told you to ... not particularly informative or logical.


Ed
 
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