piston carbon deposits

[pzi993]

I cleaned the carbon deposits from my 993 pistons and now I need to figure out something that would prevent it in the future. I was told to either polish the surface or ceramic coat it. The polishing is very time consuming and ceramic coat is about $20/piston at Pristine Powder Coating is located in Denver, Colorado .
Here is where I am at now - clean surface. Any comments?

[prschmn]

Ceramic coating generally not well advised-piston will run cooler causing more skirt wear.
since it won't expand as much as it needs to.
Drive harder------

[pzi993]

I was looking for that kind of reasoning - thanks! Correcting porsche engineers is almost always a bad idea. I guess back to 600 grit sand paper and buffing wheel...

[prschmn]

Just DO NOT polish the skirts-some texture is designed in for oil retention.

[Nine9six]

Here is some info...

https://www.google.com/url?sa=t&source=web&rct=j&url=http://swaintech.com/wp-content/uploads/2012/03/Performance-Coating-News.pdf&ved=0ahUKEwi23ImNovnMAhUG4GMKHYaFCMcQFggeMAE&usg=AFQjCNEw9CIa4XOTIaTDwhoGTePcrJWmdA&sig2=jW_L2m4HShKlZ-kzX2gDfg

[pzi993]

I am getting there - steel wool grit 0, 500grit, 800grit, 3m rubbing compound - lens buffing kit. One done 5 do go :-)

[mystert]

I ground and polished the sides of the connecting rods in my old hotrod before having them shotpeened. I used 3M Roloc discs in an air powered right angle die grinder. I used the Grey, then Burgundy, then Turquoise discs and they got them pretty shiny. Try this if you want to speed up the polishing process.

[prschmn]

Re 9962 info-good info but doesn't exactly apply to air cooled pistons and cylinders.
In a water cooled engine it's not uncommon to have .004-.005 cylinder to wall
clearance-cold-it's needed because the Aluminum has nearly three time the coefficient expansion
rate relative to steel so keeping the piston cooler allows a much smaller cold clearance-
good for skirts, etc.. But as the piston and cylinder in an air cooled engine such as a 3.6
are of similar materials the cold clearance is greatly reduced and not allowing the piston
to heat as planned means an excessive hot clearance. In order to run a coated piston crown
AND get good hot clearances you'd need to run an at least near zero if not an interference fit when cold. I expect the result of that would not be pretty.

[prschmn]

PS I do like Swain coatings when needed-been using them for years.

[jskylarwilson]

Does polishing them that much increase power, or does it make them run more efficiently?

[pzi993]

I think the carbon will not stick that much to a smooth surface.