See Figures 1 through 5
Inspect the belts for signs of glazing or cracking. A glazed belt will be perfectly smooth from slippage, while a good belt will have a slight texture of fabric visible. Cracks will usually start at the inner edge of the belt and run outward. All worn or damaged drive belts should be replaced immediately. It is best to replace all drive belts at one time, as a preventive maintenance measure, during this service operation.
TENSION CHECKING & ADJUSTMENT
See Figures 6, 7, 8, 9 and 10
Determine belt tension at a point halfway between the pulleys by pressing on the belt with moderate thumb pressure. If the distance between the pulleys (measured at the center of the pulley) is 13-16 in., the belt should deflect
Before you attempt to adjust any of your engine's belts, you should take an old rag soaked in solvent and clean the mounting bolts of any road grime which has accumulated there. On some of the harder-to-reach bolts, an application of penetrating oil will make them easier to loosen. When you're adjusting belts, especially on late model V8's with air conditioning and power steering, it would be especially helpful to have a variety of socket extensions and universals to get to those hard-to-reach bolts.
When adjusting the air pump belt, if you are using a prybar, make sure that you pry against the cast iron end