I only compared the two heads because I see they can get the same flow. But I believe the smaller port will dramatically improve atomization at 1500 rpm. I may be wrong and this is the test. But if they flow the same or similar at full lift and 25% faster than with the J heads at low rpm I'm hypothesizing better mileage and low rpm torque. 200 cfm on the intake at .450 to .500 would be plenty and I see they can get near 225. If my car was FI I would go with the J head. But beings as I require the air speed to carry the fuel into the cylinder I'm hoping these work better for my application. I picked the cam based on the ability to use Rhoads lifters and get the cam near a factory 2 barrel cam below 1500 rpm and close to a 340 mag cam fully pumped up. So in essence I'll be running a factory 360 2 barrel cam for the first 1800 rpm. This along with the small ports I'm hoping create a MPG friendly engine that has more than a 360 2 barrel engine when needed. Not trying to out run a 340 hp or anything pumped up. YET!!
