Just curious about symptoms of scored cylinders...

[afterburn 549]

That or the pistons are too oval on start up...

[Jeff Alton]

Here is one of a 3.4 Cayman S, I will take pics of the piston tomorrow as I kept it. This one has scoring on #5 and #6.



Damage is on the skirt, always the top of the bore that shows the issues (from what we have seen so far)

This 3.4 is becoming a 3.8 now...

Will be pulling a 997 3.8 motor apart shortly, I expect it will look worse based on the noise it makes....

Cheers

[KNS]

I wonder if the right time to pick up a 997 or Cayman will be another 10+ years from now? The 2.7 engines of the 74-77 911s got such a bad rap for so long but it really isn't an issue any more. By now they've pretty much all been rebuilt. One just needs to sit back and let the water cooled motors go through the process of being rebuilt (while somebody else picks up the tab).

[Jeff Alton]

The pics I posted are from a 25k mile car...

Some go well over 100K miles with no issue, some don't make it far.

At some point all motors need a rebuild, so yes, you could hedge your bets and get one that has been done with other than factory parts. But a big IMSB motor is more likely to fail from this than a failed IMSB.

I don't buy the "cold weather" issue at all. We service and have owned many local cars with over 100K miles with no issue. Yet the 40K mile 997 3.8 I own and the 25K 3.4 Cayman I own both are California cars and suffer the issue.

Cheers

[afterburn 549]

It would seem to be a EZ answer to measure the bore of cyl and OD of piston and see where the matter lays/ lies.

[Jeff Alton]

Not that simple....

It appears to begin in specific cylinders, #6, then #5, again from our experience only. Will mic and bore the next one we have apart, but micing a badly scored piston and measuring a badly scored bore is difficult....

Cheers

[RANDY P]

is sleeving an option?

if it's out of whack there's always concrete pour some of that in there.

[Brando]

Let's see pics of the pistons on that bad cyl 5 & 6.

[Jeff Alton]

Sleeving is the solution. The 2 most popular choices are Nickies or a Ductile Iron sleeve. In both cases a JE piston issued. Bore can be increased with both solutions. We have used both with good results.

Pics of the pistons coming tomorrow Brando!

Cheers

[Brando]

Thanks Jeff! My CS is in that year anx mileage range. I want to know what my options are should the same symptoms arise. A 3.8 does sound mighty nice

[afterburn 549]

Are these cylinders going oval ?
Is the cooling wrong? (heat shrink)

[john70t]

Scoring is across a general path. A lower piston path.
But the scoring is contained within specific lines.
Spread out and repeated.
Indicating a foreign singular object. Hard enough to pierce cylinder sleeves.
Oil circulation did not wash it away to the filter.

(9/26 late edit: I was referring to KNS's pic on post #15)

[afterburn 549]

you think they are picking up IMSB shrapnel ?

[RANDY P]

If it's always 5&6 and typical on engines how can it be swarf? It looks like it's gone oval.

Swarf will show up in the filter, it doesn't go away.

rjp

[afterburn 549]

Thats what I am thinking... too cold on one side, hot on the other makes for a slow egg shape.

[Jeff Alton]

It may start in other cylinders but our experience has only been 5&6...

With the frequency it seems to occur, I doubt highly that it is foreign material that got in there.

Piston pics are still coming...

Cheers

[john70t]

Piston shape?

There is a wedge relief cutout.
But on one side only.

Next to the rings at the bottom is a proud split-diverter:
Designed to transfer force cyl pressure back onto the piston head sideways.
The extra mass also holds extra heat at one specific spot.

[Jeff Alton]

Ok,

Here are the pistons from the Cayman S. Will be pulling apart a 3.8 997 S motor shortly and will post pics of it as well.









Cheers

[afterburn 549]

WOW, Bad fit for what ever reason.
I am going with the heat shrink become oval theory .
I will guess they started out with round pistons and cyl but somewhere along the lines of time
They became oval .
SO once again Porsche make a engine that is a POS?
Like mag cases. Studs made out of glass,etc

[cheeze]

Is there a sound during operation that is associated with scoring? I just picked up a 987 S and am trying to discern the differences between intake noise from valves and others. During cold starts, it almost sounds like a truck.