And, of course, the thing that must be said, and cannot be said enough: clean, clean, clean, clean, clean, any and all residue from any media blasting which might be used as part of the prep.

This thorough cleaning is required of just about any media blasting prep work, but US S3 intakes ("organ pipes") may be the most difficult ones to ensure are completely rid of residue because of the difficulty in accessing the intake runner bell mouths extending into the side plenums, creating a hiding place for sludges of blasting media mixed with old oil. Too many 928 motors have been destroyed because of leftover media.

It would be good to hear of an effective blasting media which would be safe for a motor to ingest if some is accidentally left in the intakes or cam covers.

 

@hernanca : I think that the plastic media blasting that Dr Blast does (this is who Roger works with, I believe) is safe for the engine. He's also meticulous about cleaning afterward, so that also helps.

Cheers

 

I have my cam covers powdercoated and left the plenum natural (2009):



Here's how they look now (2021):



__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

 

Thanks George
Interesting to see how the intake has aged.

 

NOTE for the people that are refinishing the intakes, powder coating is part of the refinishing sequence and the final product.
The PC layer adds thickness to the metal surface and should be restored,
this will then make the lower O rings on the fuel injectors seal properly.
NOTE use DC111 on all injector O rings and the seal on the side covers
The proper way to refinish the cam covers and the intake is to have all the gasket surfaces blasted as well as the injector bores,
then the the same surfaces recoated, along with the out side surfaces.
The same thing goes for the intake side panels the seal grooves must be smooth to give a proper seal.

NOTE the injector bore coating will usually be damaged when removing injectors that have not been touched for many years,
this will pull the coating off the bore inlet.
NOTE removal of the intake from the gaskets will also result in the PC coating being removed.

NOTE removal of the cam cover gaskets and plug gaskets can also remove the coating.
NOTE removing this coating can result in vacuum leaks that are very hard to find.
NOTE the S4 lower O rings are a special size exactly for this purpose
NOTE aftermarket O rings that match the outer ID are sometimes too big of an ID and fit loose on the injector pintle this can lead to vacuum leaks.