an unexpected find while swapping out my 911 valve covers. . .

[DavoB]

[This relates to a 1979 911 SC, ~75K mi, no recent engine work.]
So, I was swapping out my valve covers for the turbo models
this weekend, and things were going well. After doing
the more accessible passenger side cover, I started the driver side.
Upon removing the driver side cover, I heard an unexpected clink of
an item hitting the valve cover. Looking on the ground, I found the
cylinder in the photo, one side threaded, the other side with an inner hex
pattern. The cylinder, coated with anti-seize compound, had been sitting
there a while, as there is a visible ring of the silver paste
in the square-ish hollow at the top rear of the cover. As I did not see
anything amiss in the valves or other parts behind the cover, I poked my
fingers into the upper hollow and extracted the broken threaded shaft
(stud?) also in the photos, also covered in anti-seize compound.
So, from an area separate from the valve activity area, I retrieved
two items that would appear to be important to keep an engine together.
I finished the driver side cover, filled it with oil, and started the engine, and it purred, but I have not driven the car otherwise.
Where might these parts be from? I had done nothing that day to precipitate
the breakage visible on the threaded shaft, and (obviously) have been driving with these stowaways for some time. I did actually notice the threaded shaft behind and above the covers before I started the cover removal, as I was unsure what a part looking like that would be doing in that area.
With parallels to surgeons who leave sponges or worse behind in their
patients, what do I need to investigate to ensure that these "spare" parts are just left over from past maintenance?
(P.S. I now surmise that this is a cylinder nut and a stud, from parts diagrams.)

[Geronimo '74]

Broken cylinderhead stud, replace and check, or better yet, replace all the rest.
At 75k, it seems a little early, but that's what it is.
This means major work. (It is not likely to be left behind by a previous mechanic.) A good chance to perform any other necessary upgrades that have not been done yet.
Do a search on this forum on that subject, you will find tons of info. Buy Wayne's book on how to rebuild and modify 911 engines, it's a must have.
Good luck and happy wrenching.

[kidrock]

+1, the dreaded Broken Cylinder Head Stud. Best to drop the motor and replace them all with the steel ones. good luck.

[onlycafe]

at least you found a quarter too.

[McLovin]

Originally Posted by onlycafe

at least you found a quarter too.

LOL. Find 24,999 more of them, and problem solved!

[James Brown]

arrrrgg, another broken head stud! good time to bone up on your engine skills, not a bad job but something you were not planning to do. Great info on here and in Wayne's book (a must have along with a Bentley manual) If you do all your own work, it's around $1000, Good luck!

[porschenut]

Some people in other threads have commented that one or two broken studs are still okay, as long as they're not on the same cylinder, and replacement isn't usually necessary. I'm not certain this is true as I can't recall who has said it, but before you jump into an expensive repair it would be worth researching the situation to see if it's really necessary. Above all, have every one of the other studs checked.

[Steve@Rennsport]

Whenever we find a broken Dilavar head stud, we replace all of the other Dilavar ones as the others are just as likely to fail.

[Gunter]

Which cylinder?
Exhaust row?
Check all other head studs.
Get a calibrated 3/8-drive torque wrench, get a LONG 10 mm Allen 3/8-drive socket, open the valve covers, check the torque on all head studs: 23-24 ft-lbs.

You may have to drain the oil from the sump or tilt the car on one side first and then do the other side.

With only 1 broken head stud, some people keep on driving; it's up to you.
Replacing the studs is highly recommended.
It's a major job.

[chocolatelab]

i had 2 broken studs. I chose to get the studs fixed.

if its just one and everything else is fine i would be in no hurry

mileage isnt the issue for studs

its time/moisture that causes the issue.

[don gilbert]

I didnt know mine was broken until it started making a popping noise, and here is the damage, Ended up getting a complete valve job, guides springs keepers and all new valves, plus the extra mach work to true up the heads Good luck on the studs. see my thread "need help on broken stud"

[jkh2cpu]

The affected head is going to work 'loose' and no longer provide a seal between the cylinder and cylinder head, which means that you will have an exhaust leak. Let it go long enough and it will destroy the surface between the head and cylinder and fry a valve / valve seat or two in the process. Get it fix sooner rather than later. If you hear it pop-pop-popping or hiss-hiss-hissing, take it off the road. You can fix it yourself if you have the tools, the time, and the mechanical aptitude.

[KNS]

The "pop-pop-popping" and "hiss-hiss-hissing", when would you hear these sounds? Under acceleration, idle, cruise...? Very noticeable or difficult to hear?

[rs6er]

LOL I had 7 broken studs and the car ran fine. I didn't discover this until I decided to try to adjust thevalves myself.

[scarceller]

Get them all fixed, in a prior 1975 2.7L I owned this issue resulted in leaks between the cyl and the head and damaged several heads beyond repair. The leak will literally melt material from the head once it gets worse. Also if bad enough it will cause air to also leak in during intake stroke and this un-metered air will lean the mixture and could result in detonation in that cyl, it was suspected that this was what finally destroyed my 2.7L.

[jkh2cpu]

Popping and hissing? I've never heard that death knell myself, but the sage words came from Bruce Anderson. I think it hissing when cold and popping when hot, and at idle while listening near the motor. Don't confuse this popping with carb popping. Scarceller is telling you what I've read about the problem.

[DavoB]

Thanks, everyone, for the input. I am not interested in risking more damage to other engine parts, as many of you warned about, so I am selling a major organ and going to the mechanic soon for stud replacement. I value Wayne's book but I do not have the garage space, tools, or equipment to even consider taking this on.

[scarceller]

Wise choice, getting this fixed now is the best decision.

Originally Posted by DavoB

Thanks, everyone, for the input. I am not interested in risking more damage to other engine parts, as many of you warned about, so I am selling a major organ and going to the mechanic soon for stud replacement. I value Wayne's book but I do not have the garage space, tools, or equipment to even consider taking this on.

[jsmithcds]

Feel for ya man. Exact same thing happened to me. Good chioce to fix it up. Get ready for the "while our in there" expenses. I spent way to much on those....... Worth it in the end. If it's rubber replace it. Just keep in mind the 20 to 30% mark up on parts from your mechanic. Replace the easy stuff yourself to save some cash.

good luck

[Gunter]

Originally Posted by DavoB

Thanks, everyone, for the input. I am not interested in risking more damage to other engine parts, as many of you warned about, so I am selling a major organ and going to the mechanic soon for stud replacement. I value Wayne's book but I do not have the garage space, tools, or equipment to even consider taking this on.

Davo,

Make sure you go to someone who really knows these engines and issues.
During the stud replacement, insist on Steel studs, not Dilavar.
Replace all 24.
Do a valve job.
If the cams need to be reground, consider the 964-profile if you keep CIS, it has a slightly higher lift and is very compatible with the '79 FD and the larger intake runners. A 964-cam reground is only about $250.-? and you'll get an extra few horses.

Hopefully, you'll find Mahle (Nikasil) P/C's and not Kolbenschmidt (Alusil)
If the P/C's are Nikasil, just a very light hone is perfect with new rings.
If they're Alusil, re-ringing is sometimes not successful.