In 71 they didn't use a charcoal canister they vented the fumes into the crankcase by the vent lines connected to the breather. If that tube isn't connected then it may be venting to the engine compartment and that is what you are smelling.

Adding a charcoal cannister is safer as the fumes in the crankcase sometimes ignited popping valvecovers and such. In 72 the factory started using the charcoal cannisters and has ever since.