Henrique Calisto's charges had not secured a league victory since November 24, but a precious three points at the Estadio da Capital do Movel on Wednesday means that they leapfrog their opponents into 15th.
After being largely frustrated for the majority of the first half, Del Valle eased the home side's nerves by scoring the opener on the stroke of half-time.
And almost immediately from the kick-off, the hosts were celebrating again when Manchester United loanee Bebe scored his third goal of the campaign.
Olhanense needed a swift response after the break, and Paulo Regula duly provided one when he reduced the arrears on 52 minutes.
However, the visitors were unable to find an equaliser and their evening ended in further disappointment when Del Valle grabbed his second of the game five minutes into injury time.
It is just the third time this season Calisto's men have tasted victory in the league, while Olhanense have now lost seven of their last eight top-flight matches.
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