ARP Head Stud Installation - Instructions vs. Reality
 

I installed the ARP 204-4206 head studs in the case this evening, a few observations from the effort.

First a shot of a well manufactured and packaged product - they deserve to be displayed proudly on my fireplace mantle:

http://forums.pelicanparts.com/uploa...1388983141.jpg


ARP Instructions vs. Reality

The ARP instructions recommend installing the studs into the case dry (without using any type of thread bonding liquid / Loctite). I installed mine dry as per the instructions.

The instructions also recommend installing the studs "HAND TIGHT ONLY" (no kidding - in big CAPS).

I tried this but it didn't work out.

I thought that I had adequately cleaned out the threads for the head studs previously:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/786093-case-cleaning-more-case-cleaning.html

Apparently not - when I tried to hand tighten the studs, some wouldn't thread far enough in (right stud threaded as far as it would go - "finger tight").

http://forums.pelicanparts.com/uploa...1388982174.jpg


Adapt and Overcome - My Installation Process

I pulled the studs that wouldn't thread all the way and re-chased / re-cleaned the threads (blew out with the compressed air after running the chaser). No joy - some of the studs sill didn't go in as far as others when "finger tightened".

Confounded by the situation, I decided I would "HAND TIGHTEN" with a bit of leverage - I used the the Snap-On stud puller to provide the grip needed to "HAND TIGHTEN":

http://forums.pelicanparts.com/uploa...1388982515.jpg

This worked, but then I considered my next dilemma - did I tighten too much, possibly bottoming out the stud (a no-no according to many)?

Judgement call - although installing the ARP head studs to a certain thread height doesn't really matter much (uses 12pt nuts instead of the OEM barrel nuts), I decided I would install each to the recommended 135mm stud height:

I found that some of the studs would easily insert into the case proving 135mm height to the top of the threads; some required the Snap-On, "HAND TIGHTENING" method.

One last note - 143mm overall installed stud height produces 135mm height at the threads:

Overall installed length measured at 143mm:
http://forums.pelicanparts.com/uploa...1388983039.jpg

Same stud height measured to the top of the threads at 135mm:
http://forums.pelicanparts.com/uploa...1388983485.jpg

BTW - when the studs are inserted to this height, the threads are fully seated / no threads are exposed outside of the case.

There you have it - my two cents.

Gordo

Bottoming studs is really a No-No. As the case warms and expands it will generate a force on the end of the stud and try to push it out of the casing.

This force will add to the forces generated by cylinder expansion and on a Mag case could be really bad news.

I found with the bottom studs in place its much more difficult to insert the piston clips. I install top row, then the cylinder, line the pin then clip install, then install the bottom studs.
Bruce

We generally chase the case stud threads with a forming tap. This ensures a clean thread and a perfect fit. This is especially important when installing a stud in a CaseSaver.
We have the correct forming tap in stock and recommend them with every new stud customer.

M10x10.5 PD-66-N

We use a similar tap (8mm) for chasing the threads on the valve adjuster threads on the rockers

We have tended to use a thread chaser to clean cases rather than a tap.

We check the stud threads with a 6H gauge and rarely find a problem but it can be tricky to install new studs with this fit as you need to be quite fast to stop the Loctite setting.

The forming tap is an interesting idea do you know the class of fit after using a forming tap? I would guess that this will open the thread slightly and increase clearance which may make it easier to install the stud.

I have never tried to fit studs without Loctite and I would worry that they could move and bottom when the cylinder head nuts were tightened

If I bottomed out the studs, then backed them off half a turn, would that allow enough room for thermal expansion?

That's what I would tend to do as I have always been taught not to bottom studs into holes.

However, I was reading an article only yesterday about Subaru engines and Cosworth Cylinder Head Studs.

They make a stud for these engines from a H11 Tool Steel and one of the features that they advertise is a 'base seating' feature which they say is to evenly distribute the maximum load on the stud and not the thread.

The studs have a hex socket broached into one end and what looks like a dog point on the other.

It seems as if they have machined a few threads off the end that fits into the blind hole so the stud won't jam into the last few female threads and then bottom onto the dog point.

I have e-mailed to see if they will send me instructions and will talk to a couple of guys I know in their Motorsport Division about the 'base feature' and see if they believe there is a benefit in bottoming out the stud in this manner.

We have recently made some Cylinder Head Studs to suit Magnesium Cases.

We made them from an Solution Treated and Age Hardened 6AL4V Titanium Alloy (170 000psi Tensile Strength) which will reduce the pull out forces due to expansion (because of the lower young's Modulus of Titanium and its Alloys). They have rolled threads and a fine pitch on the 'nut' end of the stud.

We had a socket head broached into the stud for ease of installation but due to my belief that studs shouldn't be bottomed out we didn't consider the base seating.

http://i197.photobucket.com/albums/a...ps0ea33f9d.jpg

Just a few examples and clearly not a full engine set :)

The instructions do say that you can Locktite them in. Do most people do this? The originals are installed with locktite.

If you use loctite, apply to the threads in the hole sparingly to avoid hydraulic locking.

As far a ARP instructions - the finger tight only is standard language for their head stud kits. I've installed their head studs on other engine types such as 4CYL VW watercooled, VR6 2.8L etc... the instructions read the same. Finger tight only. As someone else stated, you only need to ensure you have a quarter turn off the bottom as long as your stud height is adequate. I.E., don't go with the 1/4 turn off the bottom as a guideline if that's too deep for the nut to thread on adequately at the other end.

This is one of the times when practical knowledge of engine assembly is useful; instructions are more of a guide than gospel. If you've been building long enough then you can know when to follow your intuition rather than written word such as OP demonstrated.

Isn't there bottoming and then there is bottoming? Certainly having the far end of the stud bottom hard on the bottom of the hole in the case is not good. But one should be able to measure what that is fairly easily. When you add that dimension to 135mm, where does that stack up against overall stud length? It should be less than 135, which means that although somehow the bottom threads may be a bit tight, at least when you install to 135mm you won't be hard against the bottom of the hole.

I think you can count on the cases being manufactured with consistent hole depths, and threaded down far enough - at least in the absence of case savers and the like to complicate things.

I have not used thread adhesive here, and I can't say that it has caused a problem. Lubricating the top threads and the washer top when torqueing is pretty much going to guarantee that the stud itself isn't going to be threaded deeper in by any significant amount, isn't it? And I've never had a stud come out on disassembly (as opposed to valve cover studs, which of course are hardly as critical).

But thread adhesive seems to work well for others, and doesn't seem to pose huge problems removing the studs when needed for machining or other reasons.

The threads in the case are not all cut to the same depth.

Porsche had a device called a "gang drill". It was a transmission that had twelve drills that would drill the case half in one operation.

Tapping was done in the same manner. The depth dimension for tapping was quite large. As a result, some studs bottom out before others due to lack of thread at the bottom of the blind hole.

The only thing left to say is it's too bad you can't see those nice shiny head studs anymore once the motors together :)

I put ARP head studs in my 3.3 turbo motor with red loctite on the stud threads.
If for some unpleasent reason you ever wanted to remove them a few minutes of map gas heat on the case around them will soften the loctite so you can get them out.

I torqued the 12 point head stud nuts as the ARP instructions said. No oil leaks and everything is fine.

I used Supertec Head Studs
 

I used Supertec Head Studs and tight the Studs by Hand.
Before I installation the new Studs i recutting all the threads to the bottom of the blind hole.
The Supertec Kit has everything you need.

http://forums.pelicanparts.com/uploa...1422098095.jpg

http://forums.pelicanparts.com/uploa...1422098113.jpg

http://forums.pelicanparts.com/uploa...1422098135.jpg

http://forums.pelicanparts.com/uploa...1422098155.jpg

I would worry about re-cutting threads as you will almost certainly affect the 'fit' of the stud and in extreme cases the load carrying capacity.

The issue is that the tap will never quite pick up on the same lead it will always start cutting in a slightly different position to the original stud.

I am not sure this is always very important depending on the engine case and the stud and just how much 'fit' has been lost.

ARP, Supertec, Casper Labs and any other stud with an increased shank diameter will increase the force on the thread produced by the thermal expansion of the cylinder.

Whilst this increase is clearly not a problem on Aluminium cases and Mag cases with Case savers I would be concerned about the thread fit on a standard Magnesium Case and avoid re-tapping the case thread other than to fit Timeserts or Case Savers.

Even with a pug tap I am not sure you will be able to cut threads to the bottom of a blind hole.

I installed ARP head studs in my 3.0 last night. When I pulled the old studs I made a tap from one of them and cleaned the threads. Every single one of mine hand threaded to the bottom by hand with very little to no resistance. I put a dab of locktite on the end, threaded them in and after hitting bottom I backed them out about 1/4 turn.

Amstaff- I suggest you quickly go check the height of your studs. It is possible to go too deep and not have enough stud rising above the stack to thread the nut on.

Head Studs Bottom Out
 

Same as far as cleaning goes:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/786093-case-cleaning-more-case-cleaning.html

Meanwhile, it was difficult to determine if the studs were bottoming out or just getting stuck as they neared the bottom.

My observation that some studs inserted to the point that no threads were exposed above the block, while some still had exposed threads clued me in to the fact I wasn't necessarily bottoming out each stud - that or the depth of each head stud hole was significantly different.

My hindsight thoughts:
- If you are using aftermarket studs (that don't use the barrel nuts / don't need to be set at a certain depth) the minor variation in stud depth probably doesn't matter a whole lot (assuming they aren't completely bottomed out).

Gordo

I would agree.

I did check the height with the cylinder in and a headin and they were perfect

Great to hear. I worried you might have to break out the torch if they were too deep and you had to fight cured loctite.

ARP info - perfect!

some more ARP info...http://forums.pelicanparts.com/uploa...1422919311.jpg
http://forums.pelicanparts.com/uploa...1422919322.jpg

I had an interesting day yesterday installing the Supertec stud kit. My case has inserts that were very clean and case was just machined by Ollies. The studs screwed in about through 2/3 of the stud thred with no resistance - even a bit wobbly. Then it became a very tight fit. The fellow at Supertec (wasn't Henry) on the phone had not run into this situation and recommended I just insert, with a ratchet, until almost all the threads were inserted. That meant only about half or three quarters of a rotation of the stud once there was any tension. The holes were certainly deeper than the inserts so I was not bottoming out. I didn't walk away with a real confident feeling about all of this but hopefully they will be ok, especially if hand tightening is all that is really necessary. Thoughts anyone?

Could be air compressing beneath the stud. Sometimes letting it rest overnight will release the pressure and they'll turn a bit easier.

Yep -

You are describing the exact situation that promted me to start this thread.

Gordo

I you consider a metric thread form the crest is always cut away and the root is rounded so there will always be a small gap. Air is also extremely compressible so I am not sure that air compression can be the cause.

This issue being described is almost certainly a result of the Fit of the two threads.

Depending on what has been done to the case threads there could be issues with the fit of an aftermarket stud.

It is quite difficult to measure the thread in the case without buying a few expensive gauges but it is relatively easy to gauge a stud.

I am sure that most studs are well made but as there is no published data available so it is hard to make a judgement when there seems to be a problem.

The Class of a thread is quite difficult to explain and I am not sure I have a complete handle on it yet as there can be variations in pitch, pitch diameter, maximum and minimum diameters and they will all have some impact on how easy it is to install a stud and subsequently how much load it can support.

I hope to have a detailed model which looks at the impact of case thread and stud thread tolerances in a couple of weeks time and I plan to write a short note on the subject.

From some basic measurements I think that there is around 27mm of well formed thread in the holes in the engine case. The hole depth is between 34.5 and 35mm and the base of the hole is rounded.

If you try to insert a stud for longer than the 27mm distance you will run into some poorly formed threads and tightening into this regions is a little undesirable but unlikely to be fatal.


Until we started making detailed measurements I has always assumed that 'extra thread' on the case end of the stud was a good idea but as we have started gathering data for an FEA Model, I am not quite so convinced.

If this is not the problem you are encountering then it could be that the thread on the stud may be a slight mismatch to the thread in the case.

The fact the thread may seem 'wobbly' with just a few threads engaged is a red herring as the mismatch will become more apparent the more threads engage.

During the last few weeks, however, I have come to the conclusion that studs with a 'base seating' feature are a good idea and once we have our model completed we hope to substantiate this belief with some good design data and design a suitable stud with all of the thread class data provided.

Love this group! Can't wait to see the details on the FEA model.
The Matco tool truck carries a relatively inexpensive thread chaser. I think I bought the whole set, m6-m10, male and female for under $30. Most well used tools in my box.

Was still unsure about my installation so I went a pulled one of the Supertec studs to compare it to the stock stud. The Supertec studs threaded area was a tiny bit narrower than the stock stud. This could account for some of the wobble I was seeing.

Stock Stud:
http://forums.pelicanparts.com/uploa...1424113877.jpg

Supertec Stud:
http://forums.pelicanparts.com/uploa...1424113942.jpg

However both had a bit of wobble when inserted into a new 10x1.5 nut, so I guess that aspect is standard.

I was also concerned about the amount of thread still showing after my install>
http://forums.pelicanparts.com/uploa...1424114050.jpg

But then I compared the threaded portion on each of the studs and the Supertec studs have a longer thread area (right end in photo below). Without this extra thread area I would have been pretty close to having no threads showing if using a stock stud.

http://forums.pelicanparts.com/uploa...1424114213.jpg

So I decided to re-blue-loctite the removed stud and call it a day. If anyone thinks I am making a mistake I'd love to know.

Gordo, I hope I haven't hi-jacked your thread. Just trying to add more discussion to the helpful thread you started....

I just noticed this thread so I'll respond to the question the best I can.
The gentleman who answered your question Terry (my machinist) is not an engine builder.
He was trying to help but your insistence prompted him to generalize without completely understanding your specific issue.
The issue is not with the stud. The issue is with the insert.
Generally after installation you need to clean the threads with a forming tap. This type of tap forms the threads to a more consistent dimension than the cutting tap that was originally used to manufacture the insert. Also quite often, the tool used to install the insert is not threaded into the insert completely and the threads end up inconsistent towards the bottom.
We offer the forming tap to any customer experiencing this type of issue.

Henry -

I would like to obtain this forming tap. The issue you describe with the inconsistent threads at the bottom sounds exactly like what I have encountered. I will contact you separately.

I looked this up just to be able to know what Henry is referring to:

Thread forming taps are designed to displace material by pressure rather than cutting the material away. Also known as cold forming taps, they have a fluteless design which is well-suited for blind holes since there are no chips to evacuate. Tool life can be three to twenty times longer than traditional taps, and thread forming taps can be run at faster spindle speeds for higher production rates at less cost per hole. Suitable for use in ductile materials without chips, such as aluminum, brass, copper and zinc - generally, materials which provide a continuous chip when drilling work well with these cold forming taps. Available in standard and Metric models.


http://i00.i.aliimg.com/wsphoto/v0/1...ing-b-font.jpg

In response to Chris' query about thread class, the Supertec head studs are built to a Class 2A using the ASME/ANSI B1.3-2007 Screw Thread Gaging Systems.

Henry,

Thanks - I guess this is equivalent to a 6g in Metric speak which is classed as a 'medium' or commercial fit and from the number of studs you have supplied clearly good enough.

We have gauged a number of 'old' steel studs and the are a 'Close' fit and better than 6g.

We have also tried some Porsche supplied new steel studs which will fit though a 6g No-Go gauge so are a lower class of fit but I don't want to buy a set of gauges to measure a 'loose' fit.

Gtg
 

Good to go Chuck,

Glad you jumped in and contributed. Saving others from similar head scratching in the future - that's what it's all about.

Good luck,

Gordo

Holy poo Henry. That was a 10 year old post!

Error

The Watson, How did this turn out for you. I have the same situation. I have case savers installed in my 2.7 and when I put the supertec head studs in they are quite loose. I believe both parts to be ok but do not fit together properly due to tolerances.

Thanks Neil

Neil. I did use Henry's thread shaper to extend good threads all the way through the case saver. They were still somewhat loose but tight after blue loctite set up. I am pretty comfortable with it due to the clamping force being what secures everything but time will tell ;-)

Thanks for the information. I thinks the studs will function very well, My main concern is I could not get them to stay tight even with Loctite and they would loosen off.