12558968 - 8.1l Waterpump Bypass Hose

Dave,

No, that is not what the waterpump bypass hose is for. Here is a description of it's purpose that I found on Hot Rod Magazines website:

All engines that run a thermostat need to have some type of bypass provision to avoid localized hot spots, minimize the chance of steam pockets developing, promote even and rapid warm-up, and prevent water-pump cavitation. On some engines, such as classic Chevy small-blocks, the bypass is internal; on others, such as your big-block Chevy, the bypass is external.