Good advice, guys. This AOS really does look like a beast. Left side, back of motor. Gotta take a lot off the top including exhaust man. to make room and even get to it. I can see why they changed the placement and form factor for 997. Wishing I had a 997 right about now...
Pelican has some incredible tech step-by articles. Check this one out for AOS.
http://www.pelicanparts.com/techarti..._Separator.htm

Next problem to solve is the Clacking. I presume this AOS issue is potentially connected to fouled/sticking valve lifter(s). I guess that's next once I resolve AOS.

 

It's hard to describe a sound accurately sometimes over the Internet, but quite a few mechanics have misdiagnosed scored cylinders as bad lifters in the past. Don't make the same mistake and borescope those cylinders first to be on the safe side instead of wasting $/effort on lifter replacement.

 

Porsche mechanic today told me the AOS would cause smoking on both exhausts, not just one. He told me to pull the sparks plugs on just the one side I have smoking on and check for a burned plug (looking), which would then indicate a valve seal issue.

Does anyone have experience (effort, cost) replacing valve seals?

 

Well, I hate to disagree with the tech but a bad AOS will tend to favor (if that is the word) one cylinder bank over the other with oil vapor at least under some conditions and these conditions are when the thing is going bad and feeding a heavy load of oil vapor to the engine.

But that's enough of that. I don't want to get too far afield from more important matters: The clacking noise.

The news the engine is manifesting clacking noise is troubling news.

I dare say with the appearance of clacking noise and the smoking combined with the build up of oil/water muck in the oil filler tube cylinder bore scoring does move up the list of possible explanations some.

But I have to also add that the clacking noise can be a worn valve stem and bad seal but this type of problem with these engines is rare. (It is a problem much more common to the air-cooled engines.)

Obviously just the word clacking is not sufficient to make any diagnosis but a proper diagnosis has to be made as to where this noise is coming from and from this then one has a pretty good idea of what's going on.

This is best done with the engine running and the car on a lift and one under the car and with extreme care -- being very aware of how close one is to the very dangerous serpentine belt and the very hot exhaust hardware -- testing various areas of the engine with a stethescope in an attempt to as best as is possible pinpoint the source of the noise.

Really this checking the engine via a stethescope is best left to a professional tech.

Regarding the suspicion of worn valve seals, while a worn/bad seal can cause the engine to smoke, my 2nd hand info is failed valve seals are rare.

But I guess you can remove the plugs. My recommendation is budget to replace these. I just do not like to reuse plugs, that is reinstall used plugs.

If you find one with the appearance that suggests its cylinder is not running right while you can suspect a bad valve stem seal you might want to use a borescope to inspect that cylinder from top to bottom. What you see or do not see determines what you do next.

My limited experience with suspected bad valve stem seals, is if a seal is bad then on the road if you lift off the gas pedal at some speed and let the engine slow the car with engine compression then get back on the throttle what you would see is smoke. Do this when the sun is low either in the AM or the PM and when driving away from the sun. If you want have a car tail your car and have a buddy make a video.

However, with the clacking noise I'm reluctant to suggest you drive the car even run the engine any as no Porsche engine ever got better when making noise from more running.

I've only replaced valve stem seals on engines with the head removed.

It is not clear to me the valve stem seals can be replaced in this engine with the head still bolted to the engine.

The general steps are the cams have to be removed. A fitting is connected to the spark plug hole and shop air is used to pressurize the cylinder and keep the valves closed. Ideally the piston beforehand would be brought to the TDC position but with these engines rotating the engine with the cams removed could have a cam chain fall off a sprocket or just slip a tooth or two and then you have big big problems.

The lifter has to be removed for its bore. Do not use a magnet!

Once the valve stem -- with the valve spring -- is exposed the valve spring is depressed and the valve spring keepers removed and the valve spring carefully removed along with any other hardware.

The old seal can be removed and a new seal installed. With the seal removed one can attempt to wiggle the valve stem about and if it has too much wiggle this is a sign the stem/guide is worn and then the head should come off and a valve job done which among other things replaces worn valves and valve guides.

The hardware removed, along with spring and its keepers are re-installed and the lifter placed back in the lifter bore and repeat this for any other suspected bad stem seals.

The above is a maybe. I'm not sure what method there is available to depress the valve spring to remove its keepers. You do not want to in any way scratch or damage the spring, its keepers, any valve hardware as this scratch can result in a stress fracture with serious consequences.

In cases where a serious engine problem is suspected -- "clacking" noises qualifies as a sign of a serious engine problem, as does the suspicion of bore scoring -- an accurate diagnosis of what exactly is going on is paramount. And this is best done by a professional mechanic. I'm puzzled why the tech would have you attempt to diagnosis this on your own.

 

IT WAS A BAD CYLINDER!


NO worst case scenario though. I was able to drive it to the shop, so my core is still good, which saves me some money. I found a long block rebuilt, resleeved on eBay and it's on its way to the shop to have my components reinstalled on it and the engine reinstalled. $11,800 or so for my full bill.

Thinking about reselling the car when I get it back. Not sure. Re-engined at 96,400. How much value does anyone think this adds?

 

Guess I called it on my first post.

If you're gonna repair it, why not just drive it afterwards?
It's pretty doubtful that you'll be able to get more than $18k tops for it.