Where should I start for more power on my 3.9 Range Rover Classic/Discovery Series I?
The main thing is to increase engine torque. This is firstly done with the ECU chipping, and secondly with the ignition upgrades we offer. For example, the Optimax or Tornado ECU Chip, adjustable fuel pressure regulator, and for the ignition, our A&R Power Amp and Magnecor plug leads, assuming your ignition (distributor) is already in good condition.
Hotwire 14CUX Tornado ECU Chip
RPi Exclusive Ignition Power Amplifier
If you wanted to make further increases in this area, then you would need to consider changing the camshaft to our Piper Torque Max cam, or increasing the engine capacity to 4.6 litre. Whether you decide the order stated here is the correct order or not, the weakness of spark and poor fuel mapping - which in itself can yield up to 30% more engine torque and efficiency - would not allow any camshaft or capacity upgrade to be effective.
Some related links
eBay Fuel Injection pages
eBay Ignition pages
eBay Engine and components pages