Allright since you cant narrow it down by sound, you have to start taking stuff apart, take the upper valve covers off first, you dont have to drain the oil, you will be able to see the rockers, and if they have came loose, etc.

Next you can drain the oil, and remove the lower valve covers, might as well take the sump cover of the bottom as well.

If you havnt found anything yet then go to the chain boxes.

Not tried it myself, but to save draining the oil in order to remove the lower valve covers, can you not jack up one side of the car, wait for oil to drain to the lower side, then remove the high side covers? Just trying to save the guy some time/effort ;)

From what I've read (think it was Waynes book), the shafts also have to be removed in the correct direction by whoever does/did the rebuild, to reduce the likelihood of damaging the housing....I know from when I removed and reinstalled mine, once cleaned-up fully including the bolt threads, they re-install really nicely. If the shop weren't diligent with cleaning and locating them on install, perhaps as Afterburn says, one has worked loose?

There is one thing that it might be.
I had a valve guide come loose in the head once.
It was riding up and down with the valve instead of the valve sliding through it.
The ridge on the guide was slapping against the head and made a really loud clack each time it did.
Not sure how you would see this with an assembled engine...but keep it in mind.
Bob

Not if he doesn't find anything, then he just wasted the time jacking up both sides of his car. It's a gamble either way but if I was doing it, I would just drain the oil and remove the sump cover first, before anything else.

Removing the valve covers is EZ enough...If it is fixable while in car, that is where to look. Other then that, engine is coming out anyway.

Hey, thanks everyone for the help! SmileWavy I have a further update.

Today I got out a couple of long handle socket extensions to use as listening devices and spent a good 15 minutes trying to get closer to the source of the sound with the car idling. This wasn't as loud in my ear as with the screwdriver, but I was also able to narrow down the location to the passenger side of the engine. So disregard what I said earlier about the noise being everywhere. Here is a summary:

Upper right valve cover: loud rhythmic clacking
Upper right valve cover nuts, especially at cylinder nr. 4: loudest most distinct clacking
Lower right valve cover: less loud but still very clear clacking
Left side valve covers: no clack
Timing chain covers: chain-running-on-sprockets noise, no clack
Block underneath near sump plate: mechanical noises but no clack


So I think I know where to go looking and I have been reading up on rocker shafts.

Question: Is it common that the heads need a re-torque in a certain number of miles after a rebuild?
Question 2: Does the AC compressor need to be removed to facilitate getting at the valve cover? Any other tips for making this job easier?
Question 3: I assume I'll need new gaskets. Silicone, or something else?
Question 4: Is there any point in doing a test with the fan belts removed at this point?


And finally, I made a short video of the clatter noise when the engine is shut off. Its the same regardless if the clutch is engaged or not, in gear or not:

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

refer to post 26
and no your heads nuts do need to be retorqued (usually) But you are looking for a sound.
i am sure it i valve related
remove covers and inspect

Sounds just like mine did with one collapsed tensioner, I'd pull off the chain covers and take a look

Thanks for the further input. It will be a couple weeks until I have time to take anything apart, so I have time to order gaskets and things. Which brings me to my earlier question. I assume the valve cover gaskets will need to be replaced, should I go silicone? What about the chain boxes, there must be a set of gaskets there too? Sorry for the noob questions-- I'll be ordering both Wayne's and Bruce's books along with the gaskets and anything else you guys recommend I have handy. I live just slightly father away from civilization then Mars, so its important to have parts in hand well before starting any work. :D

You can get by reusing the gaskets for a bit on the upper valve covers, it sounds like you narrowed it down to the # 4 upper. Likely you had a rocker shaft walk out on you.

You may have some damage but you won't know until you take a look.

The orange reusable silicone gaskets take some finesse to work, I used to hate them but have grown to like them, they work great with the right torque and making sure that the surfaces are flat, clean and dry.

Shane,

I am experimenting with the silicone gaskets now. They call out a 4-5 nm torque which is pretty light. Can you tell me what has worked for you ? The nylock nuts themselves take a bit of force to turn them, so do you add a bit to the 4-5 nm to compensate ?

Likewise, I'm now using a set of the silicon gaskets on the valve covers. I used a combination of the recommended torque for the M8's, plus a little bit until I could see the gasket squashing down. Engine's still on the stand, so a perfect opportunity to increase if there's a more proven suggestion (which I'm sure there is!...)

The silicone gaskets have to be clean and dry, the mating surfaces have to be clean and bone dry as well.

Check your valve cover surfaces for flatness, you can sand them lightly on a thick glass surface.

Put the gasket over the valve cover studs on the engine side ensuring it lays completely flat, now gently place the valve cover on, thread all the nuts in just enough so that the gap is closed.

Now turn the nuts in sequence from the center out to about 3 nm, then go over them again to full torque, the gasket should be compressed only slightly, just enough that it is even with or barely squeezing out past the edge of the valve cover. If it is squeezing out more than a thumbnail it is too tight. If you have tightened your gaskets so tight that it has left marks on the surface of the gaskets then they may leak.

So .... tighten to 3nm and then "full torque". What is the full torque specification you are referring to ? Do you compensate for the nylock nuts (which cannot be hand tightened because of the resistance of the plastic seal inside them. Thanks

possible broken valve spring?? Had that with mine.

http://forums.pelicanparts.com/porsche-911-technical-forum/467152-found-broken-parts-engine.html

Engine noise
 

Just a thought, how tight is the fan belt? If it has been over-tightened a bearing in the alternator could have been damaged. You might try taking the fan belt off and starting the engine to see if the noise goes away or stays. At least that would eliminate a possible source/problem.

Thanks for the link! Did yours make similar clackety noises before you changed the springs? Is it possible to see a broken spring without removing them? I see that the PO elected not to change valve springs on the rebuild, so of course they are suspect too. There are a lot of miles on most of my engine parts.

There was increased valve noise, but not as much as I thought there would be. Couldn't really tell if it was broken until I removed the spring.

Others (experts) told me you can feel a softer spring when the cylinder is on TDC (no tension on the spring) and you push on the spring with your hand. I used a screwdriver to get in there. Honestly, I couldn't tell. But then, I'm no expert.

Good luck.

I would think that if it originally was built with nylock nuts, the given torque would be with their resistance included.