John..

When I go to re-assemble the block....

Should the studs be torqued into the block at the same torque as the nuts are torqued to after assembly?

If I do this, the tensile stress on the aluminum should be fairly low.

Also, what loctite should be used to put the lower girdle studs in the block?

Is loctite required on the head studs?

Erik - Denmark

John,
I think this is a very relevant question, and I hope some of the expert have 'the answer'.
The shop manual did not said anything about this.
When I installed my new block, some of the studs became too low when I screwed them to the bottom, therefore I think the best will be to lock them with Loctite after measuring the height - But I am not sure

WallyP

I have never seen anything on this, so this is my GUESS.

I would chase and clean the threads in the block, and clean the studs. I would screw a couple of studs in by hand, then set the attaching part - say the cylinder head - on the block. I would then apply Loktite Stud-Lok to the studs, screw them in to the proper depth, and let them cure. Don't forget to pull the first guide studs and loktite them.

Erik - Denmark

Wally,
I think that's a good guess, but you can do it without installing the heads, just measure the free length.

John.

The studs should be bottomed out in the block....I wire wheeled my studs last night, once I get the block back, I'll do some figuring...

John Struthers

John,
I'm not sure of the specific area reference for a particular Loctite, but there have been numerous references to using 'Loctite #574' for the block in general.

LT Texan

Is someone afraid that a stud is going to vibrate loose? I wouldn't loctite it

Erik - Denmark

When I installed my new block, I did not lock the studs with Loctite, but when I later open the engine, several of the studs came off, instead of the nuts.
Next time I will lock them with a light Loctite, just to fix the studs -E.g. Loctite 222 - Remember to adjust them to the correct lengths.
Loctite 574 is for sealing not for locking

GMS

On both the 928 and the 944 block we have used Timeserts for the cylinder studs to screw into.
This prevents the "torquing the last nut and then the stud pulls out" scenario.

BrianG

This from a machinist friend: <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> The reason studs were originally used was so that there was no thread-to-casting motion during the torquing process; the motion being between the stud and the nut, instead. It was much more of a requirement in the old days when cast-iron had a lower hardness than newer alloys do. The thread friction + torque of a bolt would occasionally pull the threads out of the casting. This might be a good reason to use studs in an aluminum casting.

The proper fitting of a stud is for the stud to mate with as much of the casting thread as practical but NOT bottom in the casting. If the stud end bottoms on the casting there could be a "thrust load" placed on the casting, potentially resulting in casting failure. Instead, have the central "collar" of the stud bottom against the top thread. Proper installation is to run the stud into the casting, down to the collar, by hand and then "snug it up" with a "stud wrench" or "double-nut" technique. The clamping nut should be against a very hard surface or separated from the mating casting with a hard washer, to ensure proper torquing.

Thread-locking material can be used if frequent part removal/replacement is anticipated and you don't really want the stud to come out with the nut, but there is no other value to doing that. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I hope this helps......... <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

Danno

Uhh, the studs should not bottom out on the block. This would prevent the studs from stretching properly and will damage the threads in the block. They should be set to the correct depth and held with mild Loctite. Hopefully someone has the correct length of stud that should be exposed.

Also Loctite-574 sealant should be used on the girdle. Yamabond-4 can be used here as well.

BrianG

Danno, are you suggesting that the portion of the stud that is engaged with the threads stretches???

Steve Cattaneo

As per Dr Porsche:
“All cylinder heads are mounted with higher nuts since October 9, 1984. The nut height is now 12mm, was 10.mm.

The torque angle tightening procedures for tightening these nuts is also extended by one step at the same time.

1. Tighten all nuts to order with 20 Nm (threads lubricated with oil).

2. Tighten all nuts to order with 90 degree torque angle.

3. Tighten all nuts to order with 90 degree torque angle more.

4. Tighten all nuts to plan with 90 degree torque angle once again.

Studs for cylinder head installation are screwed into the engine block 2 mm less deep at the factory.

Remarks: The new tightening procedures extended by point 4 should also be used for repairs on older engines. A requirement for this are the, gold-yellow” studs*, which were introduced beginning with the 1983 models. The new, higher m 12 x 1.5 nuts (Part No. 999.076.028.02) should be used.

John..

Now that is good information...