Thick head stud washers on one side?

[tito911s]

During disassembly on subject car (1984 Porsche 911 3.2L) I noticed that I have triple hex head studs (964?). No the prefered options, but I see no reason why I should reaplce.

But on cylinders 1-2-3 I didn't find any washers and on 4-5-6 there (one each cylinder) very thick washers (measuring about 1/8-1/4").

Reason for disassembly were due to (1) significant leakage on cylinder 6 and head to cylinder leak.

Any thoughts on why PO did this? Anything I should be cautious of during re-assembly?

[DRACO A5OG]

That is very strange. Washers should be there or the nut will damage the heads while torquing down.

I would measure those heads studs

Post pics.

Do you know the history of who built it?

[tito911s]

Unfortunately no history. But here are some pics.


Notice the complete absence of washers from the "right" group (passenger/right side of engine), which was from the offending side (cylinder #6 leak).

Wish I could say I had documentation of the build.. . .but this time it will be done right.

[DRACO A5OG]

Edit: Never mind you wrote you suspect they are 964 Nuts,

In any case, the washers must be there. What does the studs measure out at?

I can see if studs are too short you have no choice but not to use the washers but WTF???

[tito911s]

Ok...it may be best to get very specific for measuring purposes, but washers measure 2.11 mm.

From cylinder base to end of stud(s):
Studs on passenger/right side measure approximately 142-3mm

Studs on the driver/left side measure approximately 140mm.

[DRACO A5OG]

Wait, passenger side studs are longer? We sure about this.

In any case the difference is the reason why POS skipped the washers on the shorter side. Freakin Hack.

Stock height is supposed to be 135MM, I am curious maybe POS used 964 studs? Are they longer to accommodate the 964 Nuts?

[DRACO A5OG]

Okay, was curious, confirmed those are 964 nuts.

Looking at the 964 diagram it appears 964's do not require washers.

So that means you need to lower the higher side studs by 2-3MM to allow proper seating of those 964 nuts.

[tito911s]

Cross reference: Wayne's book says 135mm. Reviewing the threads gives some interesting thoughts. 964 Head Stud Projection

This tech bulletin -- as mention -- makes it even more clear.

Based on rough measuring, my studs are long/high/whatever you want to call it, which explains why thicker washers were used. But if you look at my threads, (see below) there is still thread that the 12 point hex nut with "integral washer" could bite into for almost the entire stud, which begs the question:

Why did prior rebuilder use the thicker washers on one side? The only thing I can think of is the "integral" or open nut doesn't have enough bite?

Did he just go to sleep after finishing one side and forget to install -- or worse -- lose the washers on the other?

I guess this begs the question -- can I continue to use these head studs. Nothing I've read says I shouldn't, but....

[tito911s]

We crossed . . . but thank you. We are both on the same track. Prior "hack" lowered the side by using the thicker washers. I guess my problem is whether/not the 964 nuts have enough thread to properly seat.

This certainly explains my cylinder to head leak on cylinder #3.

I suppose I just need to figure out if hardware exists so that I can properly seat the head. My guess is that the 964 nuts don't have enough interior depth to make up the 5-8 mm difference.

If anyone knows an alternative, I would welcome it. I would like to try to not have to buy new studs just because the height is incorrect...

[DRACO A5OG]

To be safe, I would remove one on each side and measure the depth on both sides to confirm the studs can indeed go further down to spec heights.

[DRACO A5OG]

Those are Steel Studs so you could reuse them, just choosing the correct fastener after correcting the height is the key.

[tito911s]

Smart. Probably makes sense to go back to the proper M10 fastener & washer. But if I understand you right, I need to figure out how far the stud goes into the case-side to make sure I'm not bottoming out the stud, if I were to screw it in to spec (135mm) height.

Ok. We're getting somewhere. Much obliged.

[chris_seven]

I am not sure what you mean by a Triple X Stud ? The nut is defined as a 'Triple Square or XZN'

They look more like a 993 Stud with the stock 993 Cylinder head nut and I am also not sure why you would think these aren't the preferred option.

993 Studs are commonly manufactured from Dilavar which in the past has received many negative comments but I think that the resin coated studs that were supplied for the 993 have resolved these issues and should be OK.

I also believe that there was a steel version of this stud but I am not familiar with its appearance.

If the studs are Dilavar they will be non-magnetic and this should be easy to check.

If the studs are 'too short' then it means that they may have been inserted too far into the case and using a washer would be a problem.

If they have not been inserted far enough then the washers would help and it would be useful to estimate the length of thread engaged into the case.

If there is only a small difference in the measured stud length it should be OK as in an Aluminium Case there is more than enough threaded length.

It should be quite easy to find the pre-installed length of a 993 stud to estimate the length of thread in the case and once you are happy that there is enough thread engagement it should be possible to find a solution.

The easiest way out of this dilemma is to use ARP 12 point nuts M10 x 1.5 ( They are not an M8!)

The length of the stud then makes no difference and if you use a suitable 3/8" drive thin wall socket then it will all fit.

If you use the ARP nuts I would think using a washer would be a 'good thing'

[Flat6pac]

If they're non magnetic, they are 993 dilivars, approx. $45 each and preferred by some builders but expensive.
There is steel, visually identical except they are used on warercooled heads and are about 10 mm longer than aircooled dilivars.
Bruce

[yelcab1]

993 studs are 163 mm in length.

[tito911s]

Originally Posted by chris_seven

I am not sure what you mean by a Triple X Stud ? The nut is defined as a 'Triple Square or XZN'

Thank you for the correction. Yes -- triple square. And I fixed my reference to 8mm.

Originally Posted by chris_seven

If they have not been inserted far enough then the washers would help and it would be useful to estimate the length of thread engaged into the case.

This is my point. The stud measures 140mm+ from the cylinder mating surface to the end of the stud.

Originally Posted by chris_seven

If there is only a small difference in the measured stud length it should be OK as in an Aluminium Case there is more than enough threaded length.

It should be quite easy to find the pre-installed length of a 993 stud to estimate the length of thread in the case and once you are happy that there is enough thread engagement it should be possible to find a solution.

Agreed. If the nut can torque down far enough...

Originally Posted by chris_seven

The length of the stud then makes no difference and if you use a suitable 3/8" drive thin wall socket then it will all fit.

If you use the ARP nuts I would think using a washer would be a 'good thing'

Not 100% of your point here. My concern was that the prior rebuilder used washers on one side and not the other for some reason that resulted in both a significant engine leak on cylinder #3 and leakage on cylinder #6. Both problems are not the same. I know. Which is why I want to make sure I did it right this time.

[tito911s]

Originally Posted by Flat6pac

If they're non magnetic, they are 993 dilivars, approx. $45 each and preferred by some builders but expensive.
There is steel, visually identical except they are used on warercooled heads and are about 10 mm longer than aircooled dilivars.
Bruce

Just checked. They are non magnetic. So looks like you are right Bruce.

And to yelcab1's point -- this is why they are so much longer.

Any suggestions on how to get the height right? Based on yelcab1's measurement, they are approx 20mm screwed into the case. In order to get to 135mm, what hardware should I use?

[WERK I]

Those look like 993 Turbo head studs. A very good stud, but prohibitively expensive(over $19/stud!) these days. Those are 964 head nuts. The nice thing about the 964 nuts is the recommended stud height (135mm) isn't as critical. The old nuts, if the stud was slightly high, would not allow proper tightening of nut to stud. The 964 nut is open and more forgiving for slightly higher stud length. There is no need for washers, total hack job. I suspect the case threads were not cleaned out prior to inserting the new 993 turbo studs causing the stud to bottom out before reaching the proper thread depth.

[chris_seven]

I am interested to understand how a 10mm longer stud works with the XZN Style Nut.

The installed length is important as if the thread is too high above the bolting face for the head then they won't tighten correctly due to the interference with the key.

Providing there is enough thread engaged in the case then substituting the XZN nut for a standard ARP 12 point nut will eliminate this problem.

We make our own Titanium Studs and we always use a 928 Con Rod Nut as this is similar to the ARP Nut but less expensive.

They are, however a fine pitch so they don't work with a stock stud.

To fit them into the head you will need a thin wall 3/8" drive socket which has a small enough diameter and SNAP-ON socket fits easily.

I believe 20mm of thread engagement in the case is enough and if you use an ARP Nut the installed length doesn't matter - this is only important for a standard barrel nut with a key.

As the flange on an ARP nut is smaller than the flange on an XZN nut I would still use a washer but only to reduce the bearing pressure on the head surface.

The Official ARP Web Site | Kits

We also make our own head washers from 17-4PH stainless steel hardened to 42HRC.

[tito911s]

Originally Posted by WERK I

Those look like 993 Turbo head studs. A very good stud, but prohibitively expensive(over $19/stud!) these days. Those are 964 head nuts. The nice thing about the 964 nuts is the recommended stud height (135mm) isn't as critical. The old nuts, if the stud was slightly high, would not allow proper tightening of nut to stud. The 964 nut is open and more forgiving for slightly higher stud length. There is no need for washers, total hack job. I suspect the case threads were not cleaned out prior to inserting the new 993 turbo studs causing the stud to bottom out before reaching the proper thread depth.

The 964 fasteners and washers are magnetic. For illustrative purposes, it looks like the nut has about 10-12mm of thread before it starts to bottom out on whatever you are torqueing with.