PorscheLars

Scored pistons:

This is pictures (I hope this URL works) from the old 3.0 litere pistons

As you see the big damage is on the exhaust side of the piston. Every sylinder/piston look like this but with minimal damage on sylinder 4.

Why did this happend?



<a href="http://home.hpphoto.com/servlet/LinkPhoto?GUID=c8dba87f-1f7a-6ec4-565f-479e21205a3f&size=lg" target="_blank">Scored piston exhaust side</a>

<a href="http://home.hpphoto.com/servlet/LinkPhoto?GUID=6b951e18-26ea-41f3-4be2-131053502a4f&size=lg" target="_blank">Inlet side</a>

<a href="http://home.hpphoto.com/servlet/LinkPhoto?GUID=11807d63-483e-6801-20e1-546a75fa7a71&size=" target="_blank">Top and side (exhaustside)</a>

David Salama

Links only go to Hp start page. No pictures.

Perry 951

Bad thrust bearing or thrust bearing face on the crank,a ring seating problem, or a bad wrist pin. If you put a micrometer in the bore, you will probably see that it is ovaled.

New main bearings could fix it. Try that and check end play, if too much play is there, you will need a new crank. Check play on the wrist pin as well.

Sufnituning

Where can I get the measuring info?
I need also

Danno

All the measurement and clearance specs are in the manual.

John..

That is serious damage!

Matt Sheppard

Could it have been a leaky headgasket, i.e. water at shutdown leaking into the chamber(s) and washing away any oil protection? It seems to me that is why it shows up only on the "bottom" of the bore.

Brian: If it were the thust bearing or surface on the crank, wouldn't the damage be uniform from cyl. to cyl. and also show at 180 deg. on the piston?

PorscheLars

Everything else was within the spec due to clearance for the rest of the engine. I overbored and refit all bearings. wrist pins etc. No oil/water mixture detected and the car pulled good. The only way I discovered this vas lighting thru the spark plug hole and looked into the cylinder wall... I wonder if there had been to much fuel spraying on the cylinder wall in low RPM. ?

I have now bought a WBLamda sensor and will fit some K elements for each header for maximum safety and tuning.

PorscheLars

If you look at the top/side view picture it look like the fuel have washed this side

Matt Sheppard

Possibly it was leaky injectors washing the cly. down.

PorscheLars

Thank for the reply Matt
Is it realistic that all 4 injectors was leaky.. hmm don't think so... But I have heard that due reading the damage you can ecactly tell what caused this.

Is there anybody who have had this kind of damage?

May be this is a 3.0 litre issue? due to shorter skirts and or something.. As you see this is a stock S2 piston..(8 v turbo head so the exhaustvalve is on the same place as you have..

If it was heat it should be arond the whole cylinder.

If it was to much load it should be on the other side..