Internal is related to Engine. Engine can cause/lead to Energy. Energy is a different concept from Tire. Retire is a type of Tire. 
Head is related to Round. Round is the opposite of Straight. 
Internal <--RelatedTo--> Engine --Causes--> Energy <--DistinctFrom--> Tire <--IsA-- Retire 
Head <--RelatedTo--> Round <--Antonym--> Straight 