I assume:
There is good heat transfer through the piston.
And the lightweight side cut-outs are more prone to making it oval. A design flaw.

But why only on one side?
Why only two cylinders?

Some pistons are made with a oval at the skirts to help with warm up, esp forged ones...
I do not know if this is the case here or not...
The heat and cold could exasperate it.
To "heat shrink" all it takes is hot on one side and cool on the other .
If you have not ever done this you can move a mountain of metal this way.
I am going to guess #5 and #6 have the biggest variances to start .
I will also guess all the engines will encounter this problem sooner or latter.
This is not a good thing.!

Maybe kill cyl1-4 during(after) extreme cold startup? Or at least for a minute or two?

We could go on and guess all sorts of things..
But someone some where has to measure and see which one has changed (piston or cylinder

Yes,

They have a metallic tapping sound, similar to a lifter, but doesn't go away as the builds pressure, it is there all the time. The sound gets worse as scoring gets worse. It can be pinpointed with a stethoscope.

Cheers

Ah, similar to rod knock then.

Similar, but lighter sounding, more tinny, if that makes sense.... :)

Dropping the 3.8 at the end of the week, post some findings after that.

There is a good thread on Rennlist about scoring on the 996 forum called "blown engine". Discusses IMS issues as well, but a fellow there has done some measuring etc...

Cheers

What is the typical "ballpark" cost to tear down an M97 and rebuild with new sleeves?

I assume some head-work and reprogramming would be needed too.

Price all depends on what needs/gets done. LN Engineering charges 4770 to sleeve a 3.4-3.8 and supply pistons, pins, clips and rings. So add in rod bolts, gasket kits, bearings, IMSB (if you desire), chains, ramps, tensioners, water pump, valve guides, valves (if required), lifters etc plus labor to re/re engine and rebuild it. Makes most aircooled builds seem reasonable... :)

ECU will work fine with a mild displacement increase, but of course, better performance would come from a re-flash.

That V8 swap is looking mighty fine right now ;)

The V8 swap does not look good if you have ever seen the Boxster one they do.... :) We service one...

I have seen some good V8 swaps that look very clean and I have seen some shoddy ones that look like hackjobs.

Well, I think my 2006 CS is in the engine failure category. It had a few misfires this morning after warming up and luckily made it to my office very quickly.

Just started it up now, slight stumble followed by a loud clacking that increased with RPMs. Sounds just like rod knock. Fudge.

Ughh, hope it's not big ticket...

Keep up posted.

I'll see if I can snag a video later. I really don't want to run the car right now to prevent further damage.

Sorry to hear. What kind of conditions has the car been through? Mileage?

Hey cheeze, to answer your questions:

Car has been regularly maintained, oil changes at 5500-6000 miles. Aftermarket headers + exhaust. New Air/Oil separator 2 years ago, brakes & tires a year ago. Just did oil change + filters 5 weeks ago. Aside from that, just washed & waxed every month. While I have owned it, never over-revved. Only above 3k RPMs when warm.

For now, car is parked at my office. I'll see about towing it home this weekend.

So what be my options?

• Replacement engines are in the $12,000 - $14,000 range.
• Rebuild? No idea what that costs, guessing about $5,000 - $8,000 in parts + labor.
• LS7 Swap? $3,500 - $4,000 range, plus smog concerns.

Specialists or techs for the M96/M97 series that can chime in?

How many miles? Was it driven often?

I'd start a new thread here in off topic or over at Rennlist for some informative answers.

Rennlist seems much more active with the water cooled crowd for tech info.