THANKS TO: A&M Machine and Fabrication, CCTek (http://www.candctek.com), Hermance Design(www.hermancedesign.com), Paradise Road Rod & Custom, Harry Opfer Welding, Wegner Automotive Research, Clayton Machine Works
Chad we have painted alot of motors haven't had one crack or peel yet. Your going to want the surfaces to be clean! And I mean clean no silicones, oils, water, etc. No depending on how smooth you want you can de-burr the casting marks, etc. If it's just a color you want. Apply a good etch primer, followed by a sealer, then color, clear / single stage.
Most paints and clears will take close to 500 degrees so unless your motor has an issue the paint will last. We use Spies/Hecker paints and clears fyi.