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My understanding is that Ferrocoat/Ferrostan used iron particles and therefore had to be tin coated to prevent corrosion when not oiled, as you say. My understanding is that Ferroprint uses stainless steel particles and therefore doesn't need any additional coating for storage, and thus has none. My guess would be that what we're seeing in the photos is simply the Ferroprint coming off and aluminum being exposed. Everything I've ever heard on Ferroprint is that it does not work reliably on old 928/944/etc. alusil bores.
Originally Posted by Voith
The cylinder damage on rbuilt's block should be measured in depth and determined if damage is along complete piston lenght or just where rings travel.
If it's complete piston travel then I would conclude piston expansion vs cylinder/piston clearance is wrong and it's part of the failure.
The other part could be the rings which I can't see which are on rbuilt's pistons but PF's were imo wrong as all the literature I've read about alusil say rings must be alusil compatible. Which tapered type are not according to article I posted above and some other mahle/kolbenschmidt literature.
Ferrostan has protective tin layer over the actual ferrostan which protects it from corosion when pistons are new, it removes itself on the sliding part of piston and that's why all used pistons look like they have wear on the skirts when in fact it's perfectly normal.
I suspect the same protective coat is this and silver thing under it is actual ferroprint.
Yes the part with coating stainless particles was strange thought to me too. However I had a set of these new pistons and one small corner of greenish coating came off without them even being installed. Coating looked too fragile to be the actual protection. To me at least. That's why I rather opted for old tried stuff.
It would be interesting to test the silver material under the coating, maybe it is the actual stainless particles or they flaked off, stucked between rings and cylinders and ruined new engine..
The cylinder damage on rbuilt's block should be measured in depth and determined if damage is along complete piston lenght or just where rings travel.
If it's complete piston travel then I would conclude piston expansion vs cylinder/piston clearance is wrong and it's part of the failure.
The other part could be the rings which I can't see which are on rbuilt's pistons but PF's were imo wrong as all the literature I've read about alusil say rings must be alusil compatible. Which tapered type are not according to article I posted above and some other mahle/kolbenschmidt literature.
Ferrostan has protective tin layer over the actual ferrostan which protects it from corosion when pistons are new, it removes itself on the sliding part of piston and that's why all used pistons look like they have wear on the skirts when in fact it's perfectly normal.
I suspect the same protective coat is this dark green coat and silver thing under it is actual ferroprint.
It was not only were the rings travel on my engine. All clearances were spot on when measured afterwards. Also remember that rings was supplied by vendor known to rebuild these engines so have been used before. Analysis also showed rings was for alusil. Did not have that barrel shape though.
Interesting bubbling almost as if it was exposed to some kind of chemical.
Coating on my powerpak 944 pistons looked different in color and appeared to be thicker. Maybe they finished new FerroTec coating and yours is FerroTec not Ferroprint.
...uses the iron particle reinforced synthetic resin coating FERROPRINT®. MAHLE's new FerroTec® galvanic iron layer is another ongoing development ...
Interesting bubbling almost as if it was exposed to some kind of chemical.
Coating on my powerpak 944 pistons looked different in color and appeared to be thicker. Maybe they finished new FerroTec coating and yours is FerroTec not Ferroprint.
Mine looked exactly like yours and are said to be Ferroprint. Yes Bubbling is strange but to me a piston should resist engine oil. In this case Millers brake in oil and after that Millers CFS 10W60 NT.
Does anyone here happen to know, or could easily measure, the outside diameter of a 968 piston squirter? I've got an S2 block that's been drilled for squirters, but nothing has yet been installed (story omitted). Since these are special order, I'd like to confirm that 968 squirters will fit. Thanks.
Michael Stimpson of pacific performance RIP just did a S2 block for me about 4 years ago and installed the 968 squatters I bought them from sunset porsche there pretty cheap. I would think he used the same thinking on your block as he did mine which is copy of 968 block where there pointed at exhaust valve corner of piston? Sorry I don't have the exact dimensions or a extra set
Yes but for the spray pattern and distance oil must go based on stroke and location/depth of hole for engine block oil galley location the 968 squirter is really the only one that works easily without reinventing the wheel.
im almost positive Michael would have used the 968 squirter as why would you not?
03-27-2017, 01:34 PM
