PORTLAND, Ore. – The last 15 minutes of Saturday’s game felt like a prolonged heat check, a phenomenon from another sport which, after three video-game goals helped put the Portland Timbers up 4-0 on the visiting Houston Dynamo, felt apt for the soccer field. Shots from longer distances, or with more difficult techniques, fired at Joe Willis with no regard for conscience threatened to extend the night’s total beyond Wednesday’s level, when the Timbers put another four spot on the LA Galaxy in Open Cup. Over the last four days, Portland’s attack has clicked with such confidence, four has felt like less ceiling than floor.