Here is the rule for horse power, just one but an unbreakable rule, similar to the rule of gravity, lol.
The amount of air(oxygen) an engine can pump thru is what decides its horsepower, simple.
Adding more fuel simply floods an engine, so you have to add more air first, then you can add more fuel.
A 2.3l engine can pump 2.3 liters of air thru, a 5.0l can pump 5 liters of air thru, so a 5.0l engine will have more horse power because it can pump more air
If you turbo or super charge an engine your are .................adding more air, so get more horse power.
Nitrous oxide(NOS) injection does the same thing, it adds Oxygen(air) in high volume so more horse power.
So it is all, and totally, about the air the engine can pass thru it.
A larger intake can help but ONLY if current intake restricts air flow, which most don't.
All Rangers since 1986 have a Cold Air Intake(CAI).
You can convert from the mechanical radiator cooling fan to an electric cooling fan, this will free up 2 or 3 horse power and get better MPG, one of the only modifications that can do both.
But a 3.0l engine, as is, can only use 3 liters of air.
Engineering wise a 3.0l engine can make more horse power than your Vulcan 3.0l at 150HP, Fords Duratec 30 DOHC did 200HP up to 240HP with 4-valve
Last edited by RonD; 07-15-2016 at 10:52 AM.