I just put a set of aluminum vette heads on my 88' Iroc. Before the heads with a 245/50/16 tire, it went 14.49 @ 95.5 as was posted on my sig. But, with a 255/50/16 tire on the back, it only went 14.60. With the the same tire, my best last Sunday was 14.20 @ 96.97 mph. So from it was running with the 255 series tire 4 tenths is pretty good. I need gears bad and then the tire wouldn't matter so much. They are not ported, yet anyway. When I get gears I'll post more.

 

sorry not a street subject...........