Carb CFM is an interesting subject to be sure.. Just had a 327 on a dyno and here is what I learned/saw.. First the engine spec. 327 (u knew this) performer intake and Vortex fast burn heads............ With a 750 mounted @ 6000 rpm is was consuming 489 cfm .. HP was 371 . Then a 600 was mounted and again @ 6000 rpm it consumed 467 cfm.. HP 351., Looking at the numbers two things stand out, the engine never consumed all that was available (cfm) and that the larger carb did run better with a 20 point difference in air and HP. So it seems to me that the 600 cfm was not the best carb size. I understand intake charge speed but this sure adds a question mark to the general school of thought, as I see it.