Not sure what you mean by the 'down or draft' tube, but I know its called the crankcase breather / pressure ...etc. On the 216, its located by the fuel pump on the front of the motor. For some reason, ours has been modified and a freeze plug put into the hole.
Check out this pic. Its the long thingy that hangs down below the oil pan and mounts in between the fuel pump and distributor.
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http://www.adchevy.com/images/public/chevy216large.jpg[/img]
