From
Edelbrock FE Stage II - Craft Performance Engines
Edelbrock FE Stage II
2.19/1.75 Valves
28" Water 2"x6" Pipe
Lift ...... Intake CFM ...... Exhaust CFM
.300 .......... 227 ................ 161
.400 .......... 276 ................ 195
.500 .......... 307 ................ 226
.600 .......... 324 ................ 249
.700 .......... 336 ................ 265
.800 .......... 344 ................ 276
Going from 500 to 600 lift is a ~6% flow increase. Of course that is not a 6% Hp increase because the valve is only at maximum lift a short period out of the total duration time.
I did read a book on the 4.6 modular. The author claimed to have reduced the valve lift on a cam profile he was running all out in drag racing, to get a flatter torque curve for a road race car. Same duration just less lift. The dyno sheet he showed did have a flatter torque curve, but he gave up torque pretty much everywhere, which was less Hp. I do believe that at some point going more and more lift, starts giving a higher peak torque in the middle. So you may want to consult with experts -- builders who have a lot of dyno data to compare.
Just one last comment. It has been my observation that builders have to sell Hp because us consumers are unreasonable egomaniacs, who will not listen to reason. So builders are going for maximum hp and rarely look at the torque below 3500-4000 rpm. They cannot afford the time to make sure the timing curve does not came in too fast at low rpm and that is where detonation is at its highest risk. They can skip all that by starting the dyno pull at an rpm above max timing. I'm not tossing rocks here, because I do not blame them. The point being that few people are looking at the torque at lower rpms, unless they have a compelling reason. Drag racers couldn't care less.