ARP Head Stud Installation - Instructions vs. Reality

[Gordo2]

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:




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:

Case cleaning and more case cleaning

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").




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":



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:


Same stud height measured to the top of the threads at 135mm:


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

[chris_seven]

Originally Posted by Gordo2

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)?

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.

[Flat6pac]

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

[Henry Schmidt]

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

[chris_seven]

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

[gtc]

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

[chris_seven]

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.



Just a few examples and clearly not a full engine set

[Amstaff]

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

[Lapkritis]

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.

[Walt Fricke]

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.

[BURN-BROS]

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.

[JFairman]

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.

[930/66]

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.

[chris_seven]

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.

[Amstaff]

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.

[Lapkritis]

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.

[Gordo2]

Originally Posted by Amstaff

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.

Same as far as cleaning goes:
Case cleaning and more case cleaning

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

[chris_seven]

Originally Posted by Gordo2

My hindsight thoughts:
- If you are using aftermarket studs (that don't use the barrel nuts / don't nned to be set a certain depth) the minor variation in stud depth probably doesn't matter a whole lot.Gordo

I would agree.

[Amstaff]

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

[Lapkritis]

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.