GregBBRD

Yes, happens some of the time. Not a big deal. Chase the threads and proceed.

Bart-Jan

Sorry to bring up this old post again, but I have a problem:
When installing new head gaskets on my 16v Euro S, I did the 20 ftlbs and twice 90 degrees sequence as is regarded here as the correct way of torquing the heads, correct?
While doing so, I tried to measure the torque during the last 90 degrees and they all kind of finished between 50 and 55 ftlbs. When I set the wrench at 50, it didn't click, when it was at 55, the once I did on that setting didn't click. Of course, when I try to re-torque them, they are way above 55, because of the stick slip effect.

In order to prevent slipping of the ring between ring and head, I installed the rings 'dry', but put a tiny little bit of engine oil between the rings and nuts. Only enough to feel they are a little slippery; not dripping of oil obviously. Was this completely wrong? Or should it still be 3 times 90 degrees?

Ad0911

I kinda keep postponinf this job because I don't feel confident about this. There are so many differnt opinions on this theme. For instance: to chnge the studs or not? And: the short studs hould get less degrees thn the long ones to prevent overstretching. Someday I hope I will have the answer to these quetions and than I can assemble the engine.

Bart-Jan

Hi Ad,

I agree, it's still unclear...
By the way, were you at the Oldtimer grandprix at the Nurnburgring last weekend? I believe I saw your car at the Porsche stand, is that correct?

Ad0911

Wish I was. I have been there a number of times. I do not have a Porsche in running state now. Both are in rebuild right now. But there are. Number of oakgruen 928's in the dutch 928 club so I guess it must have been one of them. Was it any hood this time?

GregBBRD

There's actually some significant additonal data that we have uncovered, since this thread was started.

It seemed really strange that Porsche would make the same error (regarding head torque on the "studded" engines) time after time. Everywhere you look, in their literature, the torque specification is the same...15 0r 20nm + 3 x 90 degrees.

I assembled an '85 engine, after this thread, that had the original studs....and they seemed "undertorqued" at 2 x 90 degrees. I pulled them to the next 90 degrees and they worked fine...no issues with the studs "yielding".

Yet, the "replacement studs", from Porsche clearly yield if you try and torque them 3 x 90 degrees.

Here's my current thoughts: And this is subject to change, if the next replacement studs I get are any different than the ones I currently have been getting.

The current "replacement studs" are clearly different that the original studs. If the orignal studs are bad...or if any of the original studs are bad...replace all the studs and torque them to 20nm + 2x 90 degrees. This will end up at about 75 ft lbs...if you have a torque wrench that reads both torque and and foot pounds. (Mine reads the angle and then immediately tells you how many foot pounds were required to reach that angle....I wounld not attempt to torque the heads on these engines with any toque wrench that did not read in this manner.)

If your original studs are good (no rust and came apart without any problem....they all look the same...have the same color) torque them to 15nm + 3 x 90 degrees. (This will end up being about 75 foot lbs, also.) if you get any torque readings (after pulling the last 90 degrees) that vary more than about 10%...start over with new studs and new head gaskets....the used studs are bad.

Bart-Jan

So you suggest me to try another 90 degrees? The studs are original, look fine and currently also seem "Undertorqued"...

Do others agree with this approach? Or how about pulling the towers after a few 100 km's to re-torque?

Lizard928

For the 16V motors I do three stage torquing with the final torque value being 65.7ft lbs.

Once the final torque is achieved, I leave them for at least an hour, back them off one at a time 90 deg and then retorque

Bart-Jan

Hi Colin,

Thanks for your reply! After seeing you working on your friends car I appreciate your experience, however your approach is different to others. What is the line of thinking behind your sequence?

The last two steps is: first back all 10 of them off by 90 degrees, the next step re torque them all to 65.7 ft lbs? Or is it backof by 90 degrees, retorque and then go to the next nut and do all 10 of them after each other?

GlenL

I'm in this camp: Back off a bit and then re-torque using the old torque spec.

I'll re-re-torque if I've got time. The third and fourth times the new position is only a few degrees further indicating the gasket is fully settled.

The (older) manual calls for this with a 1-hour sitting time, IIRC!

Lizard928

Hello Bart-Jan,

it was good to meet you as well.

The manual does have a location in it that states for 16V motors with the new headgaskets the torquing procedure is a 3 step torquing process. Each way has its own merits.

Personally I like the torquing procedure as suppose to degrees as it ensures even pressure on all holding points.

When backing off 90 deg and retorquing, do this one at a time, back off, retorque, move to next. Follow torquing sequence as outlined in the manual.
..8-6-1-3-9
10-4-2-5-7
If you have time, do the re-re-torquing 2-3 times and over a period of 2 days (minimum 24 hours). This ensures that the gasket has achieved 100% crush and the nuts will not be loose after a heat cycle of two.
If you back all them off to retorque you will likely break the seal and need new gaskets.

The torquing procedure I state here is only slightly modified from the factory (re-re-retorquing). But torquing is the method stated for new style head gaskets (all you can buy now).

Lizard928

Yes, minimum of one hour between torquing sequence.
However I normally wait at least two. I would not be happy if I had to pull the cam towers off again to retorque everything!

GregBBRD

The reason almost all companies switched from "torque" to "angle" tightening was to eliminate the effects of friction on the threads and on the washer, when tightening. I was told that research had indicated that angle torquing provided much more consistant pressure on each fastener. However, angle torquing also "shortened" the time required between steps and certainly made engine assembly quicker....

That being said...I really like Colin's method, see no "downside" to it, and will try it.

I'm really tired of the different results I've been getting with the different head studs. I can see that if everything was brand new (like at the factory) and all the studs were very consistant, there would be very little downside to angle torquing. Now that this stuff is old and there is obviously some inconsistancy in studs, a good "pure" torque proceedure makes a lot of sense.

Thanks for your input, Colin!

BC

Because of head gasket compression and regular steel stretch, it seems like it may be a good idea to use as much time as is available over the torquing process.

Lizard928

Thanks for your input Greg,
I found that when backing them off 90 deg and re-torquing them, that after a couple times they did not turn further and gain degrees turned indicating that the gasket was at full compression.

Brendan,
I agree, I took two days to do the last motor I did.