This Diaphragm Pump mounts on the front all 64-73 Autolite 2V carbs as well as 64-67 Autolite 4V Carbs. With Today's Gas these commonly fail, especially when sitting for extended periods of time. Complete failure will cause dangerous fuel leaks, but many times these will affect performance well before a leak actually starts. Good idea to replace every 2-3 years or if sitting for 6 months or more.