How much will adding 16 lb to my car affect ET/mph(rotating weight)

If the tires hook the same I doubt there would be much ET difference. I've ran tires with and without tubes (less than 16lbs but still weight) without affecting ET. I broke my Sportsman/Street car and had 1 race left in the season so I took my Pro car and swapped all 4 tires around to make it legal for the class. I've ran a 31x14 (12" rim) to a 30x12 (10" rim) and car ran the same. I've tried racing front tires vs M/T sportsman DOT tires, not difference in ET.