Defender 90 3.5 conversion to 3.9 HELP!!!

I currently have a 3.5 v8 with S.U carbs coupled to a lt95 4speed manual box. I bought her as a non runner as having no spark. I fitted a new distributer and took both carbs of as she had being sitting for a while and the needles were sticking. After spending long frustrating hours trying to get her to run correctly I took her to a friend who has a far more vast knowledge than myself on v8s. After a few hours of diagnostics the conclusion was as I expected shot carbs. All the spindles have bad play in them and they are sticking open to name but a few problems! However the block is good with good compression on a test and nothing alarming on a leak test.

This left me with a few options:

1. Get the carbs rebuilt by a reputable company assuming they have the parts an expensive and dying form.

2. Keep my block and source all component parts from an Efi engine. Making it a 3.5 Efi.

3. Or source a compleat 3.9 Efi engine.

I have opted on the third option for a few reason the main ones being expense and reliability. As she is going to be used for RTV, pay and plays and is not my daily hack I need something that's a turn key motor after being sat for a week or so. Not something that requires constant attention. I feel I will get this best with the 3.9 conversion. Plus I have been offered a 3.9 with all the bits I need at the right money.

I would very much appreciate some guidance in the things am going to need to carry out the conversion successfully if possible?? So when I strip the range rover I can take all the bits I need.

Working through:

Cooling I assume should not be a problem as I have a kenlowe fan and am lead to believe that the 3.5 and 3.9 are the same "block" so all my existing heater, top and bottom hoses should fit. Would this assumption be correct??

Second the fuel side of things. I currently have the normal pick up in the tank feeding a pump that sits just behind the tank in front of the rear wheel on the chassis leg. I know I will have to replace this for a high pressure one and also change the lines. However will the pick up in the tank be ok or will I need to replace that also?? And do I need a in line regulator??

Thirdly the electrical side. The side am least confident with!! I know I need all the loom and ECU from the range rover with the relays. I have also read something about an idle control valve to allow her to tick over. However I am unable to find out any more info on how and where to fit and how it works.??

And lastly the speedo side as I understand that's different to!!? What's the best way round this and how do I go about it? Why am I unable to use my original speedo and cable or is it all interlinked with the tick over side of things?! *

And if there is anything I have missed or wildly overlooked!? *

Any help and guidance would be a huge help that I would be extremely thankful for.

3.5 and 3.9 are the same block on the outside ,there are 2 types of 3.9 with the latter having different water pump and serpentine belt ,the efi part is all self contained in its seperate loom that just needs the looms plug wiring to vehicle with an ingnition live and battery live plus feed to fuel pump all thats needed to get system working , stepper motor (idle control valve is all part of this so no seperate worry ,it will run okay without ,speedo been altered,you will need the high pressure pump to go in tank or suitable inline one can be fitted, regulator is part of engine

Only later 3.9's have serpentine belt, the early ones are the same as 3.5 although if air con fitted the alternator is on the other side of the engine because the air con compressor is located where the original alternator was (hope that makes sense).

Stepper motor is no problem, the 3.9 plenum should have it already in place.

On the speedo question, the 3.9 has an electronic speedo. The sender also sends an input to the 14cux ECU and this tells the ecu whether or not the vehicle is moving and therefore to switch on (or off) the idle stabilisation (that activates the stepper) so you will need the speed sensor or you are likely to have idle problems.

make sure you have a good clean earth for the injection loom, the injectors are switched earth. Also make sure you get all the necessary relays with the injection loom - well both relays might be more accurate - you need the main power relay and the fuel pump relay. There might be another relay ( a big green one) that is nothing to worry about as it is associated with the air conditioning which I assume you won't need.

Apart from that it should all be reasonably straight forward.

ur mad, its £250 for a pair of refurbished carbs and you are less likely to have trouble with water on your play days with carbs and also they are better at sitting unused than efi which will get damp in leccy parts. the 3.5 is lss likely to slip liners etc than the 3.9 too.

sorry to sound negative , but that my opinion after having both. also its cheaper for you and less hassel

Thanks for all the replies guys very big help keep them coming!!

theres a pump for about 50 quid on ebay (bosh one) its inline and says for the rover v8 high presure meets all req. ill be getting one for my project

classic kev said:

Only later 3.9's have serpentine belt, the early ones are the same as 3.5 although if air con fitted the alternator is on the other side of the engine because the air con compressor is located where the original alternator was (hope that makes sense).

Stepper motor is no problem, the 3.9 plenum should have it already in place.

On the speedo question, the 3.9 has an electronic speedo. The sender also sends an input to the 14cux ECU and this tells the ecu whether or not the vehicle is moving and therefore to switch on (or off) the idle stabilisation (that activates the stepper) so you will need the speed sensor or you are likely to have idle problems.

make sure you have a good clean earth for the injection loom, the injectors are switched earth. Also make sure you get all the necessary relays with the injection loom - well both relays might be more accurate - you need the main power relay and the fuel pump relay. There might be another relay ( a big green one) that is nothing to worry about as it is associated with the air conditioning which I assume you won't need.

Apart from that it should all be reasonably straight forward.

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about to do same 1993 .3.9 efi auto into into 1972 3.5 carb manual .
was planing to use 3.5 flywheel and clutch and four speed box only thing is not sure about crank sensor will it work or will it need 3.9 manual flywheel anyone know.
cheers

mal4936 said:

about to do same 1993 .3.9 efi auto into into 1972 3.5 carb manual .
was planing to use 3.5 flywheel and clutch and four speed box only thing is not sure about crank sensor will it work or will it need 3.9 manual flywheel anyone know.
cheers

Click to expand...

poss nothing to worry about looking at haynes book wiring looks like no sensor fitted ecu triggered from coil connection .can anybody confirm this cheers

hotwire has no crank sensor

fett said:

hotwire has no crank sensor

Click to expand...

cheers mal

Get on it



5.7 V8 DIESEL ENGINE GM 350 POSSIBLE LAND ROVER CONVERSION | eBay

Dr_evil said:

Get on it



5.7 V8 DIESEL ENGINE GM 350 POSSIBLE LAND ROVER CONVERSION | eBay

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I sore this

I put on a big bid when it first came up but been outbid now so thats the end of that



More money towards my welder

the early ones like that aint got much hp, the very late 6.2 is better and the 6.5 is best

should be reet in a small landy though RV8 will write off a standard box and shafts so that should too but still would put the biggest you can fit in

my bro-in-law had a RRC with the 6.2 gm derv in it, went well bags of torque.

I have a rebuilt 390 holley(manual choke) with an inlet manifold to match in good nick if you are interested.

for a deisel?

watching this thread as doing same ish swop 3.9 efi auto into 72 3.5 manual keeping man box couple of questions for you sparky experts to bypass auto inhibitor switch do i just connect yellow and black wire that goes to switch to ground .and road speed censor wires understand that yellow wire from censor goes to yellow wire in main plug in foot well. and green is 12 volt feed from ign switch
cheers in advance for any info mal

mal4936 said:

watching this thread as doing same ish swop 3.9 efi auto into 72 3.5 manual keeping man box couple of questions for you sparky experts to bypass auto inhibitor switch do i just connect yellow and black wire that goes to switch to ground .and road speed censor wires understand that yellow wire from censor goes to yellow wire in main plug in foot well. and green is 12 volt feed from ign switch
cheers in advance for any info mal

Click to expand...

theres 4 wires in switch 2 need joining to bypass inhibitor and 2 go to reverse switch