Porsche 2012 911 GT3 CUP Technical Manual page 35

8. Carefully remove the swarf and oil residue from the crankshaft bore
3.7.6.3. Fitting
If visible carefully remove small edges or burrs from the crankshaft flange
chamfer with an oil stone, afterwards carefully clean the crankshaft journal
and the crankcase bore (use cleaning solvent or acetone with a clean, lint-
free cloth).
The crankshaft flange sealing face must not, under any circumstances, be
treated with emery cloth, polish compounds or wire brushes. Remove
corrosion on the crankshaft flange with a special metal polish wad.
Afterwards carefully clean the crankshaft flange with acetone or cleaning
solvent.
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