Avec

In other cars I have had with a failing / failed PCV, yes

deilenberger

No - they are external to the combustion chamber and would have no effect, even if missing, on the compression readings.

The noise I heard sounded like it was coming from cylinder 7 or 8 - when the phone was passed toward the rear of the engine on the starboard side (passenger side in the US) and it sounded like a "clack" with a rather deep sound. It didn't sound like an injector, nor was it at the same frequency. That combined with the oil use are not good news.

Suggested action: Go to Harbor Freight - buy the "Mechanics' Stethescope" for $3.99 (unless on sale for $1.99) use that to isolate where the noise is centered. Have an oil sample pulled and send it to Blackstone - if the bore is gone that will scream in the oil analysis.. no need even to boreoscope the cylinders, Blackstone will tell you all you need to know.

TomF

I agree with Don- I hear a suspicious noise around cylinders 7 or 8 which is unfortunately where scoring seems to occur more often. Get the the stethoscope and isolate the sound. Remember, scoring in the combustion chamber will only appear when the engine is close to terminal. The real bad scoring occurs below the piston rings and can only be seen from below, which for the life me, I can't see how that can be done. A knowledgeable Rennlister claims he has a method for this but won't be kind enough to share with the rest of us...

Were any of the plugs slightly oily? My suspicion is that the plug in question will be oily if it hasn't just recently been changed. If it is, do a compression test on all the cylinders. A cylinder with scoring will be at least 20-30# off of the others.

I certainly hope that we are incorrect and it goes without saying that it is very difficult to diagnose something like this in the earlier stages via a video... A last thought- run your vin and post the engine code- it is on the build sticker in the trunk. There were a series of of engines from 2008 that seem to be more prone to scoring because of a challenged honing process and other factors.

NelaK

Wouldn't it be possible if you drop the oil pan and then work a borescope up from the bottom? You'd have to work out the positioning of the engine so the pistons are high enough and the crank shaft isn't obstructing but in theory with a fancy enough borescope it should work, right? I was looking at an ad for the fancy Snap-On scope which you can actually bend the tip on remotely.

deilenberger

I suspect it may be difficult since the engine is a semi-dry sump engine. The "dry sump" is built into the engine block, and partitioned off from the rest of the engine by baffling keeping windage from the crank and connecting rods from frothing the oil. Great design - but I think it will be difficult to get to the bottom of the cylinders. I'm not certain - but you may also have to do some serious work just to get the pan off.

I believe one of the vendors offering rebore-cylinder liners for 911 engines claims to be able to do it on the flat-6 engine, dunno if they have a technique for the V8 engines.

TomF

Hi Don, you are spot on with all of your observations above. I took to Cayenne Engine class with the vendor that you reference.

On a more positive note, the dry sump design of this motor makes it a pretty darn good engine (excepting the bore scoring, which is a manufacturing defect for all intents and purposes) and I for one really love it! It is so good that it has won at the Daytona 500... https://www.roadandtrack.com/motorsp...ts-911-flat-6/