Re-torque head stud advice.

[strikee]

- 85 3.2 Carrera leaking from cylinder head on cylinder No2. Seems like a common place for it to leak. This is not at the crankcase, but where the cylinder tower (??) meets the cylinder head. I have cleaned and verified with UV additive this is where its leaking, so please no "check the triangle of death" answers. I have also taken the covers off and find no broken head studs. The car does not blow excessive smoke or use excessive oil according to the common guide lines.

Last chance saloon thinking of retorquing the head studs.

1) Prefer not to drop the engine, can this be done in place.
2) What torque spec, considering the final part of the recommended torquing procedure is a 90 degree turn, how can you verify the current torque
3) Is it ok to do just the lowers, as the uppers are hard to get to

Your help is appreciated.

Ed

[Heinz911]

The head studs will only tighten the connection between the head and the cylinder. The tower to head connection is made with the 6 bolts (5x standard M8, 1 barrel-nut) inside the tower. Tightening of these will not stop the leak because there is a sealant (Loctite 574) between the two that needs to seal it of. In your case that seal will be broken. To properly fix this you need to remove the tower from the head. This requires removing the camshaft. This is might be possible with the engine in the car, but taking it out is not that hard and will make your life a lot easier. This job needs to be done clean and precise and I think this is hard to achieve under the car in the wheelwell.

[E Sully]

Could your rocker arm shafts be the cause of the leak?

[strikee]

Thanks Heinz, I think I used the wrong terminology. The leak is from between the cylinder and the cylinder head, not cam towers. Please correct me if I am wrong. Clearly shown in the picture. Ive read a few other threads but never found an answer as to the correct RE-torquing procedure. What ft/lbs etc.


Many thanks

[strikee]

Ed I took the valve covers off the other day, and found quite a lot of gunk. Not sure it explains my leak though. As corrected by myself - this is from between the cylinder and cylinder head.

[Heinz911]

The last picture shows a rocker-arm shaft leak like Mr. Sully suggested. The way to solve this is to fit the shafts with RS type seals.
For re-torquing the heads you should follow a criss-cross pattern starting with the middle head and moving toward the the other two. I think the torque value should be 32NM. But you should check this.
I recommend you to buy Wayne's engine rebuilding book because both the RS seals and the torquing method and values are clearly described in there.

[Lapkritis]

Leaking from the head to cylinder joint and everything intact and torqued to spec... I would guess head or cyl slightly warped. Could try cleaning and re-torquing but slim chance of success and testing aged fastener strength wouldn't be a challenge I sought after. I would live with dribble of oil from time to time rather than engage checkbook.

[E Sully]

Oil does not pass between the cylinder and the head. For oil to leak between the cylinder and the head, it would have to be getting into the combustion chamber past worn rings or guides, and loose or broken studs.
You have to realize their is a lot of air turbulence from the blower fan, cylinder deflectors, heat from exhaust, and air flow around a moving car. Pinpointing oil leaks is not always easy. Consider that oil leaking on the upper engine is going to be blown around to the lower side of the cylinder.

[Henry Schmidt]

Leaking between the cylinder and head is a by product of the Dilivar studs.
They (Dilivar studs) are an absolute design nightmare. If you try to re-torque them, you' may find many of the nuts are rusted to the studs (risking stripping the hex when loosening and tightening) and after re-torquing you risk stud fracture from the increased torque.
Unless you're ready to take it apart, I would live with the leak while you budget a major repair.

[strikee]

Thanks Henry, the picture looks like what I am experiencing. However I thought the Divlar studs were only used on the SC. Mine is an 85 which from my understanding used the steel studs.

Also I checked Waynes book, and I dont see any reference to what the torque settings should be when you re-torque after 1000kms. It mentions this should be done, but as far as I can see there is no figure to torque to. Appendix A states 20n/m and then 90 degree turn.

Not saying im going to do this, but interested to see what the magic number is.

Tks
Ed

[Henry Schmidt]

Originally Posted by strikee

Thanks Henry, the picture looks like what I am experiencing. However I thought the Divlar studs were only used on the SC. Mine is an 85 which from my understanding used the steel studs.

Also I checked Waynes book, and I dont see any reference to what the torque settings should be when you re-torque after 1000kms. It mentions this should be done, but as far as I can see there is no figure to torque to. Appendix A states 20n/m and then 90 degree turn.

Not saying im going to do this, but interested to see what the magic number is.

Tks
Ed

The 85 Porsche Carrera engine used steel uppers and Dilavar lowers. They were third generation Dilavar stud.
The only difference between the 2nd and third generation is an epoxy coating.
The factory manual calls for the same torque specification for both upper (steel ) and lower (Dilavar) studs. 1st stage 10 nm 2nd stage 32 nm.
How stupid is that?

There should never be a need to re-torque the cylinder heads on an air cooled 911 but checking it won't hurt.

[strikee]

Thank you Henry. All making sense now.

In the cars history, some of the studs were replaced, I dont remember which side it was. I will have to check.

I will live with the oil leak for now, the car still pulls like and ox and oil usuage is minimal. I might do a compression & leak down check at some stage but ignorance is bliss atm.

Cheers
Ed

[Mr Project]

Just have to say that I have a 3.2 engine that ran well, had excellent compression and leakdown numbers (3-5% on all cylinders), and it also had two broken lower dilavar head studs.

I'm pulling for ya.

[strikee]

Mr Project, I am following your thread with great interest. I admire your attitude. Along with my 911 project I am also restoring a 1978 Laverda. I dropped the bike off at a specialist for some minor electrical work nearly a year ago. I am now about $10k into it, the engine has been rebuilt top to bottom, better than factory. New rods, high comp pistons, ground heads you name it. While the engine was out "lets paint the frame and body work". While we have it apart "lets put new suspension back and front". We havent even got to the carbs yet.

We are indeed lucky to have specialists on this forum who are prepared to give up their time and answer our questions. Knowing what the right thing to do vs costs is a fine balance.

If I could get someone to whip my engine out and just replace the head studs Id do it tomorrow. Nothing else 'appears' to be wrong with the motor. However I know it doesnt work like that. I have only just start reading up on the weakness of the 3.2 rod bolts.

Car restoration is a fascinating and all engulfing subject. I hate things that are wrong or are broken, like oil leaks. They annoy me and I find it hard to ignore.

Cheers
Ed