That's true.

About 80 miles have passed since the noise in addition to several starts and idles that were performed to see if it might reappear. It hasn't.

Norm

From what I heard, and hard to really tell over the net without a stethoscope on the engine, but I would have never guessed Tensioner, but that, and or an oil pressure issue to the valve train seem only logical since it was only brief. Do have hyd or PF tensioners?

Hopefully you are done, noise is gone and aint gonna come back....

tim

OK, just because you may have dodged a bullet you should pull your case screen to inspect it for chunks of metal that do not belong there. You may have eaten an extra loose part in the internals or something became dislodged. You would be surprised how many loose small nuts, washers, keys find their way to areas they do not belong.
When they get in the power components they aways find their way to the turbine. If something gets in this pathway the turbo will show you the evidence sooner or later.
Hopefully it was only a collapsed tensioner. It happens, it's a 911.

If it happened once, it'll happen again. If it is from a collapsed tensioner, and they're not the later Carrera tensioners, put collars on the shafts as insurance.

Kids, I apologize. In true form - pointing to the worse possible scenario - I of course floated the idea that a tensioner may be at fault. Let's put all those thoughts behind us and start from scratch. What could cause valve train noise, and then just disappear? If a rocker were loose, it would not magically fix itself. If a tensioner were faulty, one would think it would stay faulty unless it pumped itself back up....which doesn't make a lot of sense.

So what gives here???? I know, maybe a plugged oil passage on that one rocker....that simply unplugged itself? But - to be honest - it sounded like more than one rocker rattlin' but damn hard to tell from a recording.

Norm, hang in there. I'm starting to lean towards something much less catastrophic and maybe just a temporary oil starvation. Hoping, anyway. So what's your plan; run it until/unless you hear that again, or take the time to pull off the valve covers and have a look-see?

At the start of the thread I mentioned I thought the sound was an exhaust or compression leak, and since Norm has ruled those out, and the sound is no longer there, I am convinced that Norm was actually "punking us" (to borrow a phrase I learned from Brandon - in reference to Robby:D), and the noise was not from the engine at all, but was actually a series of machine-gun-farts produced by the camera holder (aka, E-Normousmaximus himself). Well done, Sir!

I know what I oughta be doing, Mark, and that's drain the oil (for the third time in 236 miles), pull the valve covers and perform as good an inspection as I'm capable of. I have to admit though, that I'd much rather spend my time enjoying this wonderful automobile that's been out of service for over a year than to climb back under it for another few hours only to likely find ... nothing.

On the other hand, if there's any reasonable chance that those few hours might save me scores of others - plus, perhaps, a fair amount of money - then the idea of not going that route seems kinda silly.

Hey Norm- 964 Turbos don't have torsion bars - coilovers......

How about taking another video now that the sound is "gone" - lets hear the before and after.

Possibly you're straining with your senses as the engine is so fresh. I know I was hyper-sensitive to noises and or smells when I was in the break in phase after rebuilding my engine.

To me, it just sounds like normal noisy air-cooled Porsche valve train. As Spuggy noted earlier, unless you run the lash on the tight side, they be noisy IME. My 930 makes valve noise and has for as long as I owned it. I thought maybe it would quiet down when I rebuilt it. Fresh grind on the cams, refurbished rockers with new bushings. I had exactly the same amount of valve clatter as before rebuild. Valve train noise is identifiable by the fact that its exactly half the frequency of engine/crankshaft rpms.

Vid of my engine startup early on in the break in miles. Sound quality is perhaps not as good as yours, but I think you can hear the unmistakable valve train clatter:
<iframe width="560" height="315" src="https://www.youtube.com/embed/0UDCsEEnmVU?rel=0" frameborder="0" allowfullscreen></iframe>

My 911 race car valve train seemed really quiet to me when I got it. My first thought was, "wow, this race car engine is awesome - maybe something is wrong with the 930"

Well now I have the 911 race engine apart for rebuild and I found many of the valves were wayyyy too tight IMO. I'd rather have valves too loose that too tight...safer.

Good idea, Jacob, and you might be right about me being overly sensitive. Although I haven't actually listened to them back-to-back (I'm about to - right after getting this posted) when I heard the new one it sounded a lot of the original.


<iframe width="560" height="315" src="https://www.youtube.com/embed/lAvXAcIz4NA" frameborder="0" allowfullscreen></iframe>

So is it louder in the first video or am I imagining it?

Hey Norm, the sound seems somewhat louder in the first vid, but really difficult to say "how much" etc. . .

I hate valve clatter. I set them a snug .004

others do too.

No clatter.. none. I won't put up with it.

and it runs good.

Sounds like your valve lash is on the loose side, I'd start draining the oil and pulling the covers, there's no way that noise isn't coming back. I'd be paranoid every time I drove the car.

Well maybe it's nothing, but a wise old, blunt speaking shop teacher of mine always used to said,

"Cars don't fix themselves, if it sounds funny, it's because you screwed up. If the sound goes away, that means your screw up just got worse."

Sage advise right there my friend.

Mark

you dont have to drain the oil to pull the valve covers. i just did it about 2 weeks ago.

this JUST happened to me on sunday.
i swapped plugs and had a bad miss at idle. also heard what sounded like a plug wire acrhing.
(hi pitched popping or clicking sound). after ruling out plug wires i pulled the right upper valve cover and #6 rocker was VERY lose. i adjusted it up but had to really wonder why it all of a sudden went lose. the nut was tight.
so i looked into the oiling bar.
i put towels over each oiler and cranked it over. 4 and 5 had a little oil. none on 6. so i crnaked it up and ran it to get some oil pumping. still no oil.
i stuck a wire in the hole and as sime as i did oil started coming out. then i ranked it again and the rag had oil like the others.

point is, sometimes i could hear the rocker louder than others. sometimes not at all at idle.