Crankcase anti-seize question

[Mac-Porsche]

Rebuilding a 911sc engine for the first time. Most of the crankcase studs were removed when sending to the machine shop.

Wondering if I could/should be using a dab of anti-seize lubricant on all the various stud threads as I reinstall them in the crankcase (excluding the head studs - I know those require Loctite)?

I vaguely remember hearing/reading that anti-seize is good to prevent future stud corrosion in areas you have steel to aluminum contact?

[patkeefe]

There are different properties of anti-seize. I would get one with AL specific protection.
I don't think it will hurt to put a bit of anti-seize on there. I personally use it on almost everything.

[Flat6pac]

Head studs just torque, use lube to get good torque settings.
Same with through bolts.
Bruce

[Trackrash]

If you are talking about the 8mm studs like are around the perimeter of the case, as in installing them in the case? I would either install them dry or if they are not tightening down, a little blue loc-tite would work. I would use anit-seize on those threads that are left exposed for the nuts to be installed on.

The head studs should be red lock-tited into the case.

[Neil Harvey]

I have received 3 calls this week asking, "how to install cylinder head studs?"

My opinion is, do what ever makes you feel comfortable, or listen to those that may have some knowledge of how and why. Its up to you.

In 1 of the calls the caller was insistent that he knew best, based on how he thought "Porsche" did it and they have thousands of engineers looking into "just" how to install head studs. If he was in a deck of cards, he'd have a friend, the same!!!!

Head studs should not be bottomed out when installing. You must leave some room for the stud to turn when you torque the nut. Friction will become so high it overcomes the torque value. This way you do not stretch and compromise the threads in the case.

If you want to use Loctite, remember, you have to torque the head nuts before the Loctite cures. This is usually impossible in the build plan.

Best plan is to use a good anti seize grease, the ARP ultra is a good one as is the Extreme pressure Lube #3. You may find a slight difference in torque value with either. If the case threads are in good condition the difference will not hurt.

Do not take for granted the nuts are torqued and everything is Ok either. You may find the center nuts are not tight after you have first torqued them. Everything settles some, so do it in stages and leave for a while and go back around and recheck.

We do a small torque value on all studs to seat the heads in an order working from center out. Once we have done this, we undo the 1st nut and retorque to its final value. Repeat on all other studs. Then we leave for some time and go back and check again. Be careful of how you do this. Try always to do the final torque/angle in one movement. Also, when you undo each nut, do the full torque value in one motion.

The best method is to use an angle every time, but you will need to do some testing if no angle is given in the spec's. Some modern torque wrenches have both torque and angle displays. These are good too, but make sure they are accurate.

If the stud is put into tensile when the nut is torqued, the stud will not come loose if you do not use Loctite.

[stownsen914]

Thank you, Neil and Bruce. I was hoping someone knowledgeable would chime in and tell us the proper method.

[911pcars]

Originally Posted by Neil Harvey

........

Head studs should not be bottomed out when installing. You must leave some room for the stud to turn when you torque the nut. Friction will become so high it overcomes the torque value. This way you do not stretch and compromise the threads in the case.

Is this a comment from a customer? Hmmmm....

A stud is supposed to be stationary so the clamping nut can freely rotate in either direction. If not secured, the stud can back out while the nut is removed-NG. Thus, to secure the stud, either the stud must be locked mechanically (e.g. bottomed out during installation) or by some other means (thread locker, e.g. Loktite).

Since the crankcase head studs must be installed at a specific height for proper cyl. head nut thread engagement, they should be set in place with a thread locking material. YMMV as to brand and strength.

Sherwood

[Neil Harvey]

Originally Posted by 911pcars

Is this a comment from a customer? Hmmmm....

A stud is supposed to be stationary so the clamping nut can freely rotate in either direction. If not secured, the stud can back out while the nut is removed-NG. Thus, to secure the stud, either the stud must be locked mechanically (e.g. bottomed out during installation) or by some other means (thread locker, e.g. Loktite).

Since the crankcase head studs must be installed at a specific height for proper cyl. head nut thread engagement, they should be set in place with a thread locking material. YMMV as to brand and strength.

Sherwood

I guess I can be called a customer. I buy groceries sometimes and clothes so I guess I am customer.

Install them how ever makes you feel good. I offer my advice based on my long length of time and experience been a "customer".

nh

[KTL]

Well then I’ll ask it a different way because I was thinking the same thought as Sherwood. What is effectively happening when we allow the stud turn a bit before the friction/tension pulling on the stud overcomes the friction we experience while the nut continues to turn? Is the turning of the “free” stud relieving some of the torsional load that is being placed on the stud as we tighten the nut?

This is really eye opening for me because just the other day I saw in the 993 factory manual it states Loctite 270 is to be used on all case studs unless otherwise specified in the numerical listing of fasteners. I don’t mention that simply to defend the factory manual and thereby imply Neil is wrong. I’d like to know which is the best right way to do it.

[Trackrash]

Didn't the factory use thread locker on the head studs on the SCs and later aircooled cars? That is why you need to use heat to loosen them for removal.

The SC motor I rebuilt a while back had residue of thread locker on the threads.

[Neil Harvey]

Install them anyway you wish, do whatever makes you feel good about what you are doing. Remember, you are the assembler therefore responsible for the work involved.

Porsche did a lot of things I don't agree with. But remember, the engine was first assembled with the thinking it would never come apart.

You can use any sort of thread locker goo but be careful of how and when you tighten the head nuts. As I have SUGGESTED, use this stuff but be sure to tighten the nuts before the goo goes off.

You open the chance that the goo breaks and your toque wrench will snap and now where are you for torque valve or angle. Also, the torque valve will change with different goo.

My suggestion was to put the studs in with some anti seize. Install until they bottom and then do a 1/2 turn approx. out so they are not bottomed. If you want to make sure if they are in at the correct height, fit a cylinder and 1 head and check. Simple check.

Now when you either torque the nut or torque and angle tighten the nut, the stud can move until the friction takes over. You are not stretching the threads in the block. Ever wondered why the studs are hard to remove? Many times the threads have deformed in the block. Your torque wrench will keep turning until the friction takes over and now the wrench will stretch the stud.

Who cares if the stud comes out when you undo the nut!!!!! Really this is a concern? Not in my world. I'd be happy if the studs came out when undoing the nuts. That would save a lot of time in a rebuild. Once the nut is tight and the stud in tension, the nut will not come loose. God forbid, every rod bolt would be coming loose too.

This is not hard stuff. Its simple stuff to understand and to do properly an easy exercise.

But again, do it however make you feel good.

[Trackrash]

Even though Loctite claims to fill the gaps in threaded fasteners, you have a good point about torquing before it dries.

[stownsen914]

What would be the purpose of using Loctite on head studs where they screw into the case? Do they have a tendency to unscrew themselves from the case? I've not heard of that.

[KTL]

Well I learned something new. So yesterday was a good day.

Incidentally the 993 steel studs I bought back in 2011 came with dry threadlocking compound applied to the case stud ends. I thought that was odd. Maybe that stuff cures a lot slower in the absence of air and would allow the stud to turn when tightening. But I took weeks to build that engine so the stuff certainly cured before I got to installing the heads

[911pcars]

Originally Posted by Neil Harvey

I guess I can be called a customer. I buy groceries sometimes and clothes so I guess I am customer.

Install them how ever makes you feel good. I offer my advice based on my long length of time and experience been a "customer".

nh

Neal, Would that be considered a "hunch"? YMMV, but it doesn't sound very "tech" to me. Studs, if not firmly set in place, can back out due to repeated cylinder and cylinder head heat and cooling expansion cycles as well as vibration. Porsche head studs are normally threaded to a spec'd installation height.

Factory case threads or thread inserts are not designed to be "used", otherwise the factory would have used bolts. Thus a thread locking device is needed to maintain that stud ht. spec. With clean, undistorted threads and lube the cylinder head nut tightening torque (~32 Nm/25 ft.lbs.) isn't high but enough to adequately clamp and seal the components.

Sherwood

[Neil Harvey]

Originally Posted by 911pcars

Neal, Would that be considered a "hunch"? YMMV, but it doesn't sound very "tech" to me. Studs, if not firmly set in place, can back out due to repeated cylinder and cylinder head heat and cooling expansion cycles as well as vibration. Porsche head studs are normally threaded to a spec'd installation height.

Factory case threads or thread inserts are not designed to be "used", otherwise the factory would have used bolts. Thus a thread locking device is needed to maintain that stud ht. spec. With clean, undistorted threads and lube the cylinder head nut tightening torque (~32 Nm/25 ft.lbs.) isn't high but enough to adequately clamp and seal the components.

Sherwood

That was my poor attempt at being sarcastic.

I give my advice based on how we do certain procedures. We base these on experience, engineering and a requirement that we have no failure issues as we receive a monetary reward for doing this work.

This advice is free and if you do not want to take it, that is completely Ok with me. I’m not responsible for your engine and is integrity. If you feel that the use of some sort of locking is required when installing head studs, then do it. I have no problem with whatever you do.

To your points though, I offer the following. Which end of the head stud do you think see more heat? Which end of the head stud see more vibrations?

When you tighten a nut or bolt, you do several things in this procedure. First, you close the gap between the under side of the bolt or nut. Once there is no gap between these and the surface been clamped, you will not change this distance. What you will do is to stretch the bolt and or collapse the clamped surface.

So, think about tightening the nuts on the cylinder heads. Once the nut surface contacts the washer surface, (let’s call this the head surface), the two are in contact and the distance between the two will not change. Now turning the nut further, either by a torque value or angle, you are putting the stud into tensile (stretching it). It then becomes like a stretched spring, putting the clamped surfaces in tension.

Why do you think the end of the stud that is in the case would come loose before the head nut? The fact is, neither will if installed correctly, care taken, and everything checked.

This is not rocket science and there is not “one way” here either. You must decide which way you feel is best. You are the engine assembler, so you are responsible.

[911pcars]

Is your experience derived from building Mg engines? If so, you’d understand that Mg threads shouldn’t be overly used, especially after many years in service. I think Porsche engineers realized that reality.

The theory of a stud is to fix one end in place, then use a nut on the other end to apply assembly torque. You are correct in that torque tension is equally applied to the entire stud, but since the fixed end (in the case) doesn’t/shouldn’t move, there’s minimum friction between the case and stud threads. The long term integrity of Mg case engines relies on the strength of those case threads.

Material longevity was expensively revealed when the factory, in order to meet US emission regs., installed engine components and instituted tuning mods that also increased the normal operating temperatures. The resultant increased running temps increased thermal expansion that compromised the strength of the case head threads. The rest is history.

Subsequent repair techniques (case savers and equivalent) use steel inserts to strengthen this weak point, and aluminum was then universally used since then for engine cases. It’s not a torque accuracy thing; it’s merely material life.

Studs are still used to reduce thread wear, even in aluminum engine parts, to attach valve and chain box covers, cam housings, exhaust components, etc.

Or perhaps a shorter answer (should have started with the following):
https://www.reddit.com/r/AskEngineers/comments/16zgqs/when_should_i_use_a_stud_vs_a_bolt_ie_my_exhaust/

“studs help ensure that your engine block isn't damaged in routine maintenance by externally threaded fasteners that are harder than it is.”

As in all opinions offered in this forum, YMMV.

Sherwood

[Neil Harvey]

"""Is your experience derived from building Mg engines? If so, you’d understand that Mg threads shouldn’t be overly used, especially after many years in service. I think Porsche engineers realized that reality."""

No, but if you are actually interested in my experience, there is a little blurb about my history etc on our web site. performancedevelopments.com – Engine Design.

Not that it should matter any.

In reality, studs fixed in the cases often do move when the head nuts are torqued. They "snap" and you have now lost your torque value or your angle measurement. If your are fitting any stud into any engine part made of any material and did not check the integrity of the thread, then you have not done your assembly job properly. Any threads should be of quality enough to withstand the fitment and tightening of any stud or bolt. Period!!!

Humbly stating, we do this procedure based on our own experience on multiple engines and applications, which is firmly entrenched in basic engineering and common sense.

As I have suggested over and over, if you want to Loctite the studs into the case and if this "lifts your skirt, go ahead and flash the world".

[Mark Henry]

Supertec studs came with loctite copper anti-seize for the nuts, IIRC the studs used locktite thread sealant. Other engines I've used ARP rod bolt grease just because it was handy.

[911pcars]

Originally Posted by Neil Harvey

"........

In reality, studs fixed in the cases often do move when the head nuts are torqued. They "snap" and you have now lost your torque value or your angle measurement.

Not sure what “snap” describes. Does that refer to actual stud failure as early and counterfeit versions of Dilavar did? Or does that describe thread sealant failure? Stud failure is obvious, whether the stud threads are “floating” or fixed in place with sealant. If the thread sealant fails when torqued, the case threads then carries the frictional load during additional tightening of the stud. Same objective with that caveat.

”.... If your are fitting any stud into any engine part made of any material and did not check the integrity of the thread, then you have not done your assembly job properly. Any threads should be of quality enough to withstand the fitment and tightening of any stud or bolt. Period!!!

I agree, but that’s not the same issue we’re discussing. However, if threads bind within the head nut range, then the stud/nut acts as one assembly, IOW, a bolt. Should be okay as long as the stud doesn’t bottom out. If the nut thread binding isn’t recognized as such, the stud then uses the case threads to hopefully achieve the required tightening torque. Same issues with procedures that call for removing a bound stud/nut. Perhaps it’s an overall wash in terms of proper head clamping despite a compromised stud/nut interface.

”.... and if this "lifts your skirt, go ahead and flash the world".

AKA YMMV. At the same time, it’s only a preference in component assembly within our relatively small bubble. As it applies to clothing, shorts are not in a bind.