cylinder to head leak.

[fastfredracing]

How often do you guys see leaks at the cylinder to head interface. Last 3 motors I leaked down were leaking here, and no signs of pulled or broken studs. The last one I did appeared to be a fairly fresh rebuild. I guess maybe a strong argument for retourquing the heads after run in

[Eagledriver]

Does a retorque stop the leak? What kind of motor? I had a Carrera that leaked there but the leak was so small that it could be lived with for a long time.

-Andy

[fastfredracing]

I wouldnt count on a retourque to stop the leak, but after a rebuild, a retourque may prevent it. The latest is on a 2.7. I pulled the bank of heads this morning, and two of the upper head studs came out while turning the head nut. The case was timecerted, but there was no loctite on the studs threads. These two studs felt considerably more loose than the others. The ce ring was split, this cylinder was leaking about 40% so I figured it prudent to address this

[911 tweaks]

not to derail here, but... are we supposed to re-torque the head studs after a re-assembly? AND if so, when and how/what is the procedure??
Thanks!
Bob

[BK911]

Do you mean like this?



'80 3.0. 12% leakage at the head gasket. 3 head studs were loose.

[fastfredracing]

Exactly, and the last one I saw was on a 3.0 like yours. I assume you replaced the ce ring. I just thought it was weird that I had 3 motors in a row like this.

[RSstop]

I rebuilt a 3.0 and two heads were loose & leaking with erosion around the ce ring. All 24 head studs were dilivar. This car was used mainly on the track.
I rebuilt the top end using 993 studs. No signs of loosening after 2 years.
What kind of head studs were in these cars?

[fastfredracing]

The 2.7 had steel studs, I was up at the shop tinkering last night, and I found that I could literaly unwind some of the head studs with my fingers, No loctite whatsoever. THe 3.0 that I did had dilivar, and had some broken studs, but still had a leak on a cylinder that had all 4 studs intact,

[Mo_Gearhead]

Tweeks, Mixed signals here. They are discussing stud problems, but yes, you should re-torque the head NUTS after a rebuild. 300-500 miles (street engine).

[Henry Schmidt]

This is a perfect example of why we designed our own head studs.

Supertec head stud kit. Available from our host.

[Eagledriver]

I was looking through my factory workshop manual today for engine break in procedures. The have a procedure to tighten the nuts on the headstuds after the run in on the dyno. That's the first I've heard of Porsche recommending a retorque on the heads. I typically haven't done this.

-Andy

[911 tweaks]

what is the procedure to "re-torque?" Is it loosen all then re tighten OR just check tightness with torque wrench at the final max spec amount? (My guess is the later)...if that makes me a smarter guesser OR does all of this depend on the brand hear stud?? :-)
Bob

[Eagledriver]

The verbage in the factory workshop implies that you only check tightness to the specified torque.

[911 tweaks]

Thanks Andy for the answer. For some reason my brain was thinking crazy thoughts i.e. to loosen all up and then retorque.

[safe]

Originally posted by Henry Schmidt
This is a perfect example of why we designed our own head studs.

Supertec head stud kit. Available from our host.

Are the supertec studs steel or some other kind of exotic alloy, like dilivar?

[304065]

Magnus, Henry posted the materials composition here:

supertec headstuds-anyone used them?

[safe]

Thanks John!