After reading many threads on the subject... I'm just confused. I'm using a 5L block with studs (yellow ones) and 16v heads.....

do i do the,

15 ft lbs
90 degree
90 degree...

or do i do another 90 degree?

 

I do 2 90's. I tried to do 3 90's on an engine into which I had installed brand new studs and "yielded" about 80% of the studs. (I have a torque wrench that angle torques and then tells you, after you are done with that angle, what the resulting foot pound reading actually is. I actually had less torque on 80%of the fasteners after 3 90's than I had at 2 90's. Carefull inspection of the studs showed that they were actually "necked down" in the middle....yielded....junk.)

Thinking that Porsche must always be correct in what they print, I figured I had done something wrong, so I bought another brand new set of studs and repeated the same process.

Again, about 80% of the studs had yielded and were "significantly longer" than when they started.

I looked carefully, through all of the Porsche literature and noticed than none of the other models (944/951/968) ever used more than two 90's...even though the hardware, head, and block are virtually the same. I also found literature with the instructions to only do 2 90's on the 928 models.

I bought another set of studs and torqued them to 2 90's. Been doing that, ever since, and regardless of what anyone thinks or says, believe that to be the correct proceedure.

As an interesting side note to this.....I've do quite a bit of research into this "problem". ("Research", for me, means that I study the problem first hand....I don't go to the internet and see what other people think.) I've found that "old/used" studs are much stiffer....they seem to loose their elasticity with age. (Note that this is also true of the vehicles equiped with head bolts....they do not "stretch" as much when they are "old".) Most of the "older" studs (now most all 30 years old) seem very happy with 3 90's....however the "resulting torque values" are very high (sometimes over 120 ft lbs.) and I'm concerned that the threads in the block will "pull" with "initial" torque values this high, once the engine gets hot. I also believe that the design of the studs are such that Porsche wants the stud to "stretch", but not yield. I believe that a stud that is "stretched" puts better "crush" on the head gasket throughout the entire heating cycle than an "unstretched" stud. (Which is why I believe that the ARP hardware doesn't work...it is too high of a grade to properly stretch and provide the proper "preload" to the head gasket.)

The result of my research makes me install new studs in virtually all of these very old engines...and makes me buy new head bolts for the engines that use them.

 

And some people wonder why your engines work so well Always informative.

 

So, Greg, what is the torque reading range that you get?

 

well did the 25ft first, then 90, then 90. some were seemed tougher then others, but i got no washer spin (marked them).

so I'm done? or do i wait an hour and do the 1/4 turn loose, then re do it?

 

Just me, but I'd say you were done.

As for torque readings, I've seen them all over the map so I've stuck with the 20nm/90/90/90 for studs and 20nm/90/90 for bolts.

 

Excellent timing for this post, and great info and insight as well, thank you.
I picked up new studs for the 86.5 eng refresh and a digital torque / angle wrench from Eastwood.
When setting the studs into the block I'd seen a light coat of oil is recommended by some, is that true?
Thank you,
Dave k

 

Jake
We are talking about your 16v 81 right
If so My WSM from Porsche Canada shows
As follows
16 valve
Nm /ftlb
1st step 20 / 14
2nd step 50/ 36
3rd step 90/65
Or

1st step 20nm/2ftlb?? ( I think this is a typo)
2nd step 90deg torque angle
3rd step 90 deg torque angle

Up to model year 84

then

32 valve

1st step 20nm/14 ftlb
2nd step 90 deg torque angle
3rd step 90 deg torque angle

No mention of a 4th step anywhere

Interesting that in 77 before the wsm were printed they spec 61.5 ftlb wait ½ hour then retorque to 61.5 ftlb

 

when i read older posts they talked about the re-torque after the wait time elapsed. but per Greg, i went with option 2.

 

I didn't retorque mine after doing 15 and then 3 90s. I wish I had only done 2 now. Either way, it's been fine since reassembly a couple years ago.