Jamescw

http://www.photodump.com/Jamescw/2007-09-18/

please view these pictures, I took the cylinder head off to replace stem seals, guides and do a valve job. What i found was the quench area of the piston and the top of the cylinder head where it meets was mangled... I have no pics of the head right now its in the shop... but has anyone had this happend before, it appears all pistons had come into contact with a foreign object that damaged it pretty good. No signs of piston trouble were noted before the head was taken off. I pulled head because intermittent smoke/burning of oil ( assuming stem seals). Help! Dont mind the scraping i did of the center of the piston, look at the bottom of the piston where it is swarfed.

ddg=shinebox racing

Pistons look the same as mine.
It almost looks like somebody dropped a ball bearing into the cylinder!
Are they all like that??

Jamescw

2.2 L, so if it was just 1 cylinder i could maybe understand, but they all have it so i dont know what went through the engine or what is falling apart.....

Katman

Whatever it was, it looks like it happend a while ago, as the dents look just as crusty as the rest of the pistons.

Very odd. Doens't look like much damage, compared to what you'd get if you dropped a valve.

Mabe pull that piston, and see if anything going on with the rings too..?

Otherwise, (from the pictures, anyway) I can't *really* see why you couldn't polish up the piston to removed any sharp edges on the dents, and continue on..??

AudiSport4000

Yeah, very strange indeed...

Supercoupe

I'm on a small portable pc, but it looks like it could be old remnants of detonation, maybe someone had the timing advanced too much and didn't hear/didn't care about the pinging.

Jamescw

Well the concensus seems to be that it is from detonation, pretty amazing if thats the case, but couple people ive chatted with assume thats what caused it considering its only in the quench area of the piston.... Iam going to polish it up and continue on with the valve job, head will be decked enough to hide most of the damage on it.... the compression was down to 110 - 140 at the highest measurment, hoping for all sakes that a valve job can jump it up past 120 for the lowest. just too lazy to continue with new pistons / rings as the bores look so fresh still. wait and see i guess

4000fixes

Maybe somebody had put in those nasty Bosch +4s. The heat index is too high on those plugs... +3s 4Life. lol.

Katman

If detonation, you may want to pop the pistons out to take a look at the rings.

From what I understand, rings take a beating under detonation too.

You would *really* kick yourself it the low compression was due to broken rings, and you never checked them when you had the head off.. :-)