To install I use a 100 watt light bulb. Just put the new pulley directly on the lit bulb for 15-20 minuets. This should evenly heat it up so that the hole is large enough to slide on to the shaft of the alternator. On larger things that need a shrink fit I use a oven to get it expanded. There should be about .002" interference between the shaft and the pulley if not it will slip on the shaft. Not all alternators have the same shaft/pulley size.