Fabio421

I have a brand new set of pistons for a 4.5L engine ( 95mm ) but when I pulled them out of the box it appears that there isn't any coating on the skirt. As far as I know, all 928 pistons were required to have the Ferrostan coating and it was a dark grey/black colored material. Am I crazy or do these pistons look uncoated?

Lizard928

Look coated to me.

namasgt

They are coated, are these the set Mark was selling?

danglerb

If they seize in a few hundred miles they may not be coated.

Other than visual, is there a an easy test to check them? I'm thinking find a spot that isn't important, and mess with it a little, polish it or something and see if it looks aluminumish.

Lizard928

Those are coated. That is not bare aluminium.

Fabio421

I've always been under the impresion that the coating was dark in color.

Lizard928

Nope. It isn't. At least none of the ones I've had have been.
This goes from NOS 97.5mm pistons, to 4.7, to S3, S4, and GTS.

Fabio421

OK, cool. Thanks

Strosek Ultra

Try a magnet.

Ake

GregBBRD

They are coated.

BC

I had a new set of those as well many years ago when I built a 4.5L new. Those are indeed coated - and probably old stock so its the old way - where the entire piston basically got the coating prior to machining the rings and pin bore (and maybe valve reliefs)

toofast928

Flash washes out the pic. The coating on my pistons and head chambers are light gray. Their should not be a question if coated or not. One can just tell.

Vilhuer

Dark coating is aftermarket stuff used by Wössner etc. Its only applied to skirt area,