Thread: Disco series II Bosch plenum to series 1 3.9l

Hi Guys.
I have this Disco series II plenum (the Bosch type), but dumb me did not know it will not fit a 3.9 series I inlet manifold. I have found a wrecker in the USA that is willing to sell me a series II manifold (bare) at a reasonable price.

The thing is, will all the bits off my series I fit it. Such as fuel rail, pressure regulator, and what about the stepper motor? What else will I need?

I got the throttle body and bracket bits with the plenum.


I would appreciate the help here.
By the way my contact in the US has never heard the term "Inlet manifold"

There is quite a bit of fabrication needed.

I had a machine shop machine out the water outlet to fit a 3.9 thermostat housing using one of the threaded holes and drilling and tapping 2 to suit.
There was a dummy boss on the manifold which I drilled out shortened and threaded for the water temp sensor.
I used my TPS from my 3.9 by adapting the throttle spindle and using a bit of nylon breadboard as a spacer.

The RRC 3.9 fuel rail fitted with a bit of modding around the mount tabs. The 3.9 RRC rail with the fuel regulator on the drivers side will fit but AFAIK the Disco one with regulator on the LHS will not. I also had to cut off the mounts for the coils to use the standard regulator.

I made up a base for the stepper out of nylon breadboard and attached it to the manifold with heater hoses. I also made a bracket to mount it at the back so the wires would be long enough. I had to make up an inlet between the MAF and throttle by aralditing a hose into a length of silicon hose.
The hardest most time consuming was to set up a kickdown cable. I had to custom make an actuating arm to fit on the throttle spindle, then the outer cable holder. The kickdown cable was lengthened by HSV Rangie's idea of making up a intemediate bracket to mount the original cable to and then crimping another cable on using bicycle brake cable.
The MAF on mine now is not attached to the air cleaner but to the silicon tube by a clip. I do not know how it works with a flat panel air cleaner as mine has a barrel.
Be careful to drill a hole in the bracket for the kickdown cable under to throttle body to allow to adjust the small allen key for base idle. the Thor does not need base idle adjustment as it has a much more powerful idle control than 14CUX. It is a very sensitive adjustment.
For The heater hoses I used the original Thor outlet which has a pipe with O ring and tab to hold it on and fabbed up the othe rpipes from my RRC pipes and used the original inlet? on the back of the water pump.

If you get stuck just PM me and I can take a photo of my solution , which you may think is crap but has worked now for about 4-5 years without a major problem. You can use the original throttle cable by cutting it shorter and silver soldering a new nipple on.
Regards Philip A