So I'm trying to figure out what I want to do about pulleys and I have a few questions. My engine came with a 3 groove crank pulley and no belts. What are they all for? As far as I know I have the alt, water, and AC. I figured the alt and water pump both use the same belt. Which leaves another one for the AC, so whats the third for. Next question is I have an alternator bracket that has an idler pulley on it (pic included). What was that for?