In the sentences you gave, and in general usage as a conjunction, there is no difference.
However, consider:-
1) using "whenever" as an intensive form of "when" in a question.
("Whenever will that dog stop barking?")
2) as a substitute for "at whatever time that" or "when".
(Q. "When can we leave?" A."We can leave whenever you're ready".)
In the examples above, "whenever" cannot be substituted by "every time".