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Flapper to MS conversion - Things I learned along the way

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I now have my '88 Range Rover Classic running on a Nige MS kit and thought I would put together a few of the oddities I came across during the conversion that I struggled to find information about, I may well cover things that have already been documented (but I didn't find), if so I apologise, and this is simply my experience of the install...

Fitting the newer top end assembly, mine came from Nige and was originally off a 3.9 engine (others may differ), the differences to the original flapper that had to be overcome were:

  • The feed from the thermostat housing to the heater matrix is in a different position (3.5 is at the front, bottom right, 3.9 is on the left hand side of the housing), originally I though I could just move the fitting to the '3.5' postion (as there is a blank in the 3.9 in that position) but they are different threads!? In the end I shorterned the fixed pipe and cut the original rubber hose to suit the side position fitting - As below


  • Throttle cable linkage - the linkage that came with the 3.9 top end required the throttle cable to enter from the right hand side, there was no way my existing cable was going to reach as on the flapper linkage it enters at the back of the plenum. So I used the flapper linkage but this then made it tricky to install the PWM valve, although with a bit of jiggling is did fit and not foul any of the linkage etc. I couldn't however fit it on the nice bracket that comes in Nige's kit.
  • I had to blank one of the larger vacuum ports on the left hand side, there was a couple of blanks in the kit but neither were the correct thread, so I ended up cutting the barb off the fitting I wanted to blank, drilling and tapping it then screwing a bolt into it (with some thread sealant)


The fuel pump installation required cutting a hole in the boot floor (or dropping the tank), which I did, I will look up the dimensions that I found and add them to this thread later.

The rest of the hardware installation was pretty straightforward, although the screws provided for mounting the coil pack bracket (the two through the waterpump) did not have enough thread cut on them, they bottomed out on the thread way before they came out of the back of the waterpump housing, I ended up running a die down them to extend the threads, once I'd worked out the thread type, I think they were a UNC (maybe UNF) thread and they were both different sizes, just to make it more interesting! off the top of my head I can't remember the sizes, I will find out and update.

Installation of the ECU itself was pretty straight forward, for simplicities sake I have fitted it in the same postion as the stock ECU, under the drivers seat, not ideal from a wetness point of view but I intend to build it into a waterproof box in the not too distant future. I screwed the ECU and relay board to a piece of MDF that then bolted to the the original ECU mounting positions I also fitted a screw terminal rail to use as an earth point for the main ECU earth, Lambda heater etc.



Rightly or wrongly (please tell me if its the latter) I wired the orange PWM feed to one of the Inj 12V points on the relay board, it appears to be working ok, also I earthed the EDIS unit back to my earth rail (not an ECU earth), again, seems to be working fine. These were both best guesses really as the wiring diagram wasn't 100% clear,

I also drew this up to make wiring the relay board up easier...


Hope this is of some use to anyone undertaking the conversion and I will add to this thread as more things come back to me!



Edited by Mattsuffolk

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Good info!

I'd point out that you can swap the 3.9 fuel rail & injectors onto a 3.5 Flapper inlet manifold which makes the plumbing / throttle cable differences go away.

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