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I've got a 98 navigator with the 5.4 SOHC motor.

how can I make more power, while still running 87 octane, and not making the car much louder?

What free mods are there and such? Wanting to do little stuff that doesn't cost much. Say.. $500 max budget.
 

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One of those Superchips tuner things? I'm sure they make them for all Ford trucks, but have never used one so not sure they're any good......just an idea and I think it's in your budget.
 

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JamesN1830 said:
I've got a 98 navigator with the 5.4 SOHC motor.

how can I make more power, while still running 87 octane, and not making the car much louder?

What free mods are there and such? Wanting to do little stuff that doesn't cost much. Say.. $500 max budget.
For $500, just keep it in best running condition as possible: fresh plugs, use synthetic lubricants, K&N drop-in filter, lower temperature thermostat to keep the heads a bit cooler, save up for lighter mass tires (generally cheaper 2nd tier brand tires are heavy) since $500 won't get you new tires and above. These mods (except lower temp. thermostat) will over time pay for itself due to the Navigator's thirsty nature and rising fuel prices.

Doing an exhaust or FULL intake mod will probably do nothing if not hurt a heavy SUVs real world low-mid speed performance. If you want to stay 87 octane, then there may be no use in getting a chip retune because chip makers often (Hypertech I recall did have lower octane tuning) exploit higher octane and narrower safety margins to gain torque and power. Even then a 1998 model in 2006 will likely have enough engine deposits to even make gains on high octane with "cookie cutter" retunes questionnable.

Heavy rides like yours do respond well to ring and pinion ratio increases. Check your rear axle ratio and see if any upgrades exist for it. This is going to be a seat of the pants felt improvement. You will need to recalibrate your speedometer (few ways to do this) or else your reading will be higher than actual speed and your odometer will log extra ficticious miles. Another drawback is lower highway fuel mileage and possible increases in noise from gear whine if it's an aftermarket gear set and/or incorrectly installed. If you have 3.73 gears, check if you can get a 4.10 gear set from a Ford dealer (there may even be great OEM Ford parts deals in some Ford performance mags.) since I doubt OEM ring and pinions will be noisy.

I don't know about tire options, but a less intrusive/easily restorable way to increase your gearing is to use smaller overall diameter tires fitting on the same rim. That plus seeking out the lowest tire mass in its size class will result in measurable improvements. You definitely won't have gear whine issues but speedometer recalibration issues apply.
 
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