Your cam overlap and exhaust backpressure have a big influence, though
Definitely.
Correct backpressure for blower: zero. If his BP exceeded his boost level he was using iron single exhaust with a bad muffler.
Any improvement to the head or exhaust will reduce boost and increase power. Boost means there's an obstruction.
There's a correction for overlap that can be plugged in to the formula.
1. Take nominal overlap (not @ .050").
2. Deduct 30° (Vizard's correction for ramps in a hot cam).
3. Multiply result by .01
4. Subtract from boost pressure (it's leakage).
Example: overlap is 70°, deduct 30 = 40°, × .01 = .4.
I prefer to move it around:
B = ((ratio × blower capacity × 2 × atmospheric pressure) ÷ engine displacement) - (atmospheric + O/L adjustment)
Example, using 230" + M90 @ 2 × engine speed, overlap is conservative at 50°.:
(2 × 90 × 2 × 14.7) ÷ 14.7 = 5,292.
Divide by 230 = 23.01.
Subtract (14.7 + .2) = 8.1 psi.
