1997 Defender 90 - Power Upgrade

1997 Defender 90

One of the most common Defender upgrades we fit is the 4.6 liter long block. Any Defender owner knows that there is a lot of shifting to be done as soon as big hills are encountered either manually or automatically. The problem gets worse if large tires have been installed. The owner of this Defender had installed 285/75/16 which are 33.2” tall.

To compensate & improve over stock we installed a 4.6l long block, reprogrammed the GEMS engine management & regeared the axles with 4.10 ring & pinions. While installing the ring & pinions we also installed ARB locking differentials.

Here you can see the new 4.6l long block on a stand waiting to get all the manifolds, fuel injection & ancillaries swapped over.

Once the 4.6 was assembled it was installed in the vehicle.

The 4.6l engine runs slightly warmer than the original 3.9 & 4.0 engines. Air conditioning compounds this problem because not only does the condenser slow down air flow through the radiator but it generates more heat. If a radiator is not in perfect condition we replace it & whenever AC is fitted we put holes in the back of the bonnet to allow air to exit the engine bay more easily. If a vehicle is going to operate in an extremely hot environment all the time we have several other modifications we make to prevent overheating when sitting idling for prolonged periods.

The 4.10 ring & pinions & ARB air lockers are installed. The 4.10’s change the gearing so that with 33” tires the motor is turning at 3100 rpms in top gear at 70mph. Peak torque is generated around 3200 rpms. This means less shifting on hills.

We believe that a vehicle is only complete when every little detail is the same or exceeds the way the vehicle left the factory. When changing final drive ratios this means the speedometer is no longer accurate. We have a kit of parts that work with a programmable speedometer so that the speed & mileage is correct.