Note this is different than the Chevy setup where the riser part of the road draft was retained minus the draft tube and with a threaded boss from which the tube routed through the pcv valve and then over to the intake. The better setups used the air cleaner to replace air removed from the crankcase, although the vented oil filler cap on the rocker was also used. These tend to get blocked off with gummy grit and grease fairly soon. grin