Engine power is a function of the air it can use and the compression it can use.
SOHC had more power because Ford increased the compression ratio to 9.7:1, the OHV was 9.0:1
But when you raise the compression above 9.4:1 Regular gas(lower octane) will start to self ignite(pinging/knocking), so Ford added a Knock Sensor.
When running regular gas the Knock Sensor detects the self-ignition and advances the spark timing to ignite the air/fuel mix before it can self-ignite, this reduces the power output of the engine, but it would still have more power than the OHV because of the higher compression ratio, just not 40HP more, closer to 25HP.
If you just add more fuel to an engine all you get is a flooded engine, no extra power, less power in fact.
You need to increase the air, the more air an engine can use the more fuel can be added so the more power it can get.
This is why a 5.0 liter engine has more power than a 3.0 liter engine, it can use 2.0 more liters of air every 2 RPM, so more fuel can be added.
A larger Cam can allow engine to pull in more air, so can increase power.
A turbo or super charger gets more power from an engine because it forces more air into the engine so more fuel can be added, so more power.
Nitrous injection(NOS) is the same as adding more air, you can use more fuel.
Stroking an engine increases engine size, i.e. changes a 4.0l to a 4.3l, so more air
So bottom line is "There is no replacement for displacement", a Bigger engine.
If you were racing in a 4.0l class then spending money to increase 4.0l power would make sense, but other wise, no, you can of course use a bigger Cam, turbo or supercharge, increase compression or stroke it.
But in the long run and for a daily driver a stock 5.0l V8 would be a better choice, IMO.
Exhaust is about scavenged power.
Using smaller pipes at the heads and then dumping them into a larger pipe(collector) will cause a Low pressure at the head(exhaust valves).
What this does is pull exhaust from the cylinder when exhaust valve opens, which means piston doesn't have to push as hard to get exhaust out of the cylinder, so less power is taken away from the crank, leaving crank with more power for rear wheels.
This low pressure is in the design of the headers, it can be at lower RPM, mid-RPM OR High RPM range, but only one range, most headers are designed for low range.
Ford uses mid-range on Rangers, yes you have a tuned exhaust now.
So headers increase available power by using low pressure to pull out exhaust.
This is also where the MYTH of engines needing back pressure comes from.
People would install larger pipes on the head and lose power, so they think "engine must need back pressure"..........wrong
What they did was to eliminate the low pressure created by the smaller pipes dumping into the larger pipe, so they lost that extra scavenged power.
No 4-stroke engine runs better with back pressure, 2-stroke engines do, but that's another story
Last edited by RonD; 08-09-2016 at 02:23 PM.