T supra 87

Ok I just got a 1987 toyota supra about a month ago and the heater does not work I've tried everything I can think of. Ok so I have replaced the heater core, blower moter, heater control valve all of the hoses and the thermastat and all it does is blow air that is the same temp outside I have tride flushing the system and nothing is cloged everything is wired up corectly and have cheked to make sure all the water hoses are hooked up corectly and checked all fueses and I still have no heat... I have takin it to my friend who is a mecanic and he looked at it and it stumped him he can't think of 1 reason that it wouldent work please help some1