Dreaded Dilavar Disaster Diverted ??

[Jerome74911S]

Pfut-pfut-pfut-pfut. That was the Porsche music that I heard the other day on acceleration. It was loud and scary, and since I have been hearing a peculiar noise during my last several rides, naturally I assumed the worst - a Dilavar Di$a$ter.

I had just put fresh oil into the engine, and being too cheap to dump it for the sake of an exam, I jacked up the car on the left side (allowing the oil to run over to the right) and took off the lower valve cover. All the studs were tight

Then I jacked up the right side and waited for gravity to move my oil to the left. It was difficult to stuff a camera in there, but the bottom of the #6 cylinder looks like this:



Next, I applied a magnet to each stud, but none of them would pull out:



To double check, I applied an 'L' shaped hex wrench to each stud and they all seemed snug - until I got to the last one at the front of cylinder #6. (This is one of Murphy's more reliable laws.) It turned. %$!?&! Using the hex wrench was awkward, so I applied Porsche Special Tool #JK-050416 to that last stud:



Backing the stud out didn't seem to go very quickly, so I thought, "What if the thing has simply become loose for some odd reason?"

Therefore, I began to tighten it. In a few small turns it snugged up! Giving an extra bit of a turn on my special tool made it seem quite snug.

Is it possible that the stud could have loosened? Or did I somehow simply tighten the broken piece against whatever remains in the crankcase?

Please tell me that it only needed tightening . . .

The '75S engine was rebuilt at least ~6 years ago (less than 20,000 miles [32,000km]), using second-generation gold coloured Dilavar studs.

[Discseven]

J... nice that you found loose stud. And good inspection. Am hoping with you that turning did indeed tighten. You gona torque it?

It's possible pfut sound is not cylinder related but exhaust. Can be blown out exhaust gasket in which case there'll be a soot marker indicating the leak---but perhaps not easily seen with an installed engine. Or, might be at any exhaust flange. Same soot marking occurs so long as the area is protected to a degree.

Soot marker:

[RSTarga]

never loosen a stud. never retorque, now you have to retorque that one. With a proper torque wrench. The best way to check is to lightly try to tighten, if it doesn't turn you are ok. Normally just leave them alone.
Good luck.

[Rawknees'Turbo]

Jerome, were you able to tell if it was the stud or the nut that was loose? Regardless, you will know if you truly got lucky if it stays tight.

PS, it looks like you have one or more rocker arm shafts that are walking out of their bores - will need to address that right away.

[RSTarga]

^^^^Yikes! sharp eyes.

[Jerome74911S]

After I invent yet another tool (welding something) to extend a hex wrench so that I can get a torque wrench onto it, I will re-torque that stud and hope that it stays put.

On the right side of the engine, which is now up in the air, all of the exhaust flanges look clean and shiny.

When possible, I'll examine the flanges on the left.

And, I will have a close look at those right side rocker arm shafts! My photos from the left side of the engine suggest that those are all properly in place.

[chris_seven]

Jerome,

Why did you use a magnet? Dilavar is an Austenitic Alloy and is non-magnetic.

If the studs attract a magnet in the same manner as a conventional steel stud then they aren't Dilavar.

There is a discussion that Dilavar does have a small amount of residual magnetism but if you look at the detail of the alloy composition this should be almost non-existent.

Some Austenitic Stainless Steels do develop magnetism due to the transformation of retained ferrite caused by cold work but the high Molybdenum content of Dilavar should supress this behaviour.

If the studs are strongly magnetic they aren't Dilavar.

If the stud has loosened then you need to understand why the Threadlocker has failed as this seems relatively unlikely and would be worrying.

If the nut has come loose then you need to understand the reasons. If it has held correctly for several years then it seems unlikely that it has shaken loose.

It seems more likely that the stud has lost preload due to the thread in the case.

Has the case had Timeserts of case savers fitted? If not the thread may have pulled very slightly and the preload has been lost.

I have to say my natural instinct would be to worry.

If the case hasn't had inserts you could just re-torque and keep an eye on the situation and it if loosens again you will need to look more deeply into the problem.

If it does have inserts I would spend more time and look more closely.

[theiceman]

he used a magnet because the nut is steel. .

any how I would concur with getting in there and looking closely. if you torqued it up and the stud has come through the barrel nut further than the others its an easy way to tell your stud is pulling. Each stud ends at a specific high above the case in order to have the barrel nut torque up and have the stud in roughly the middle . if yours is approaching the end and you have less room to get your hex in you are definitely pulling that stud out of the case.

interestingly I had a broken dilivar for a while and did not hear that exhaust note at all . I would think if you hear that there is more than one loose

[Trackrash]

As chris_seven mentioned did you have case savers or inserts installed during the rebuild?

If not I think your stud pulled out of the case.

Good luck, and keep us informed.

[Jerome74911S]

Originally Posted by theiceman

he used a magnet because the nut is steel. .

any how I would concur with getting in there and looking closely. if you torqued it up and the stud has come through the barrel nut further than the others its an easy way to tell your stud is pulling. Each stud ends at a specific high above the case in order to have the barrel nut torque up and have the stud in roughly the middle . if yours is approaching the end and you have less room to get your hex in you are definitely pulling that stud out of the case.

interestingly I had a broken dilivar for a while and did not hear that exhaust note at all . I would think if you hear that there is more than one loose

Yes, my blue handled magnet is stuck to the nut in my photo above. I will try to attach a skinny magnet onto the center of the stud itself to see if it sticks there. I re-examined my older photos, and I'm not now sure about the stud's colour.

As well, I will determine whether or not the stud is further into the nut, as you mention.

Can I tell from looking somewhere (with the engine in the car) that the engine has Timeserts? I thought I was able to see them when the engine was out, but that was a few years ago. The engine was rebuilt before I got it.

[theiceman]

no you will not be able to tell , documentation of the old rebuild might show it but outside of that I think you are out of luck .

I sure you know the 74-77 were prone to pulling out the studs of the mag case so it would give me cause for concern.

[Trackrash]

If you had the motor rebuilt and it had not been rebuilt previously, you could check your receipt from the machine shop to see if inserts were installed.

Anybody IMO who has any experience working with 911s would know to have case savers or timecerts installed on any mag case motor when possible. My machinist installed case savers on my motor in 1983.

I don't know how you can tell by looking at an assembled motor to see if they are there.

[Jerome74911S]

Originally Posted by Trackrash

If you had the motor rebuilt and it had not been rebuilt previously, you could check your receipt from the machine shop to see if inserts were installed.

Anybody IMO who has any experience working with 911s would know to have case savers or timecerts installed on any mag case motor when possible. My machinist installed case savers on my motor in 1983.

I don't know how you can tell by looking at an assembled motor to see if they are there.

Thank you for your interest and commentary; I do appreciate it.

Note that I said, "The engine was rebuilt before I got it." Perhaps I also should have said that it came in the car without receipts. However, the engine was pristine looking everywhere, top and bottom, plus it had Carrera cam chain tensioners, SSIs, a Dansk muffler, and other stuff that I have forgotten. True, this equipment is mostly external, but since the engine came from a different car and was so completely tended to I imagined that everything that a mag engine usually needs was tended to. I could be wrong, of course.

[Trackrash]

I have read several accounts of head nuts coming loose.

[Jerome74911S]

Originally Posted by theiceman

he used a magnet because the nut is steel. .

. . . if you torqued it up and the stud has come through the barrel nut further than the others its an easy way to tell your stud is pulling. Each stud ends at a specific high above the case in order to have the barrel nut torque up and have the stud in roughly the middle . . .

As I said above, I have to invent an extension in order to properly torque that stud, but after temporarily making it good and snug (maybe even too tight), the stud was exactly in the middle of the nut, same as the rest of them.

From this observation it seems to me that the stud was indeed loose for some reason. The Locktite, or whatever, didn't hold - maybe. In any case I feel more relaxed at this point.

Now to get those rocker arm shafts loose so that I can properly center them. They are really tight - anyone know how to safely pop them loose?

[Rawknees'Turbo]

^^^

Jerome, what you describe above would indicate to me that the nut was loose, not the stud (which is much better, btw). If the stud were loose, the nut would have been as well (unless locked in place with corrosion) and when you tightened them down, the nut would have moved quite a bit and the stud thread would not be in the same spot as you can see on the other studs/nuts.

Regarding the rocker shaft bolts - you'll have to get in there with a 1/4" drive ratchet (a wobble/swivel head works best) and an alan socket that you've cut down to fit.

[chris_seven]

Originally Posted by theiceman

he used a magnet because the nut is steel

Doh!

[red 2.7]

Jerome
Back to the original problem of the Phutt Putt sound. Is 1 loose nut enough to create the leak? Many people have reported driving for a while and discovering 2 broken studs. Also it's good to see that you can fix being "off your rocker" . ;-)

[Discseven]

Originally Posted by red 2.7

Jerome
Is 1 loose nut enough to create the leak?

Good point of debate Red.

[prebordao]

Some years ago I had my engine rebuilt and some of the studs (maybe half of them) were pulled.
At the time, the "pfut" sound was clearly audible when cranking and when shutting down. Not much (or even nothing) while driving.
I would say that just one loose nut isn't enough for such a clear sound...