Just to give you a real example, My 331 made 548 hp - 455 torque @ the flywheel on 105 octane. Peak hp @ 7200
Basic specs:
solid roller / not radical
Roush intake with 750 cfm
Yates heads fully ported to my combination
R-302 block
0-balanced rotating assembly
10.5:1 compression
Major work with windage &
oil pan
There is another 100 hp in this motor if I up the carb, cam & compression. 650 hp would be max for these heads naturally asperated. By the way, I would not call this a street motor.
I have 18 to 20k in my motor and as you can see, naturally asperated, a 302 starts to push the envelope at the 550 range.