You can add at the very least one second to that time. A Fiat 124 Sport 1600 could do just over 17 secs and that was with twin cams and carbs and at least 10 hp more with similar weight. More than just about any other car I can think of at the time, the 124 was almost directly comparable to a Celica GT (not the LT) has the totally usless Toyota OZ knobs elected to import it here.