i have a set of 4 screw s.u.'s on my 240 with a n-36 intake. i came across a very nice set of 3 screw s.u.'s and was wondering if they would be any better. i had heard that the 3 screws were the ones to have. thanks for your help,tim
4 screws are the ones to have assumong the needles are stock. they are the earlier 240z carbs. from 70-early 71. these have better performing needles in them as they did not have to worry about emissions quite as much. bottom line, if both are tuned perfectly the 4 screws will perform better. in the real world, whichever set is in better shape will make your car the fastest.