Quote Originally Posted by auxiliary
they're the "same"

blacktops have cooling fins on the block/head right under the valve cover.
The difference is that the black top s13 motors were made 94 and up and s13 red top was made in the earlier car. When they decided to extend production of the s13 chassis they had already changed the color for the valve cover and decided to make them black top to denote the generation of s13. The s14 black top has the hump in the valve cover.