How difficult would it be to put a 4.0 in a current 3.9 1995 Discovery

[atancreti]

Hello all,
I am thinking about putting this 4.0 that I have been through into my 3.9 1995 discovery. The current engine runs awful and ticks and clanks! lol How much would be involved in converting the land rover to the 4.0? Obviously computers... But what else. Lets say time and money really aren't issues... But we want to do it less than 1k. I already have the engine and computer, I can get wires for cheap if I need them. I posted this on other forums as well! Thanks!!!

 

[psykokid]

The main thing is that the 3.9 to 4.0 designation is more of a badging change to differentiate the distro motor from the GEMS coil pack motor. Same displacement, IIRC the main difference between the two is the front cover for distro vs coil pack. Having not done it personally, you should be able to swap the 4.0 motor in and change a few parts from your old motor to the new one and run the new motor with the current distributor based EFI system. If you want to move from the distro setup to the later coil pack system later on down the line its certainly something you can do and shouldnt be that big of a feat to accomplish..

 

[ipgregory]

It’s not quite as simple as just the motor and the computer. The wiring on the 2 vehicles is almost completely different with respect to everything to do with the engine and most of the dash. This extends to other things like the fuel pump and so on. Many other things are similar but have different connectors on them. You’re going to run into this all over the truck. You will either need to get the full guts from a 96 or you’re going to be doing a lot of splicing and adapting all over the place.

While theoretically possible it’s a lot of work and not something I would do to just change the motor. I would modify the motor to work in the 95 truck as was suggested above. They are essentially the same motor with a different front cover and more sensors on the 4.0 that are not needed on the 3.9. Luckily the 95 Disco is a serp motor so it has the same crank and so on, just has a dizzy and a different intake system. Change over the plenum, the wiring/sensors needed by the 14CUX and the front cover and you are most of the way there.

Only reasons I can see to do this is if you wanted to tune up the motor and wanted to utilize the stronger bottom end of the 4.0 or you already have the motor and want to flip it for a bad 3.9 as you suggest.

My recommendation is to leave the 96 GEMS stuff alone and/or sell it, use the 14CUX setup that you already have in the 95 and save yourself a lot of headaches.

 

[I Leak Oil]

I personally think going to the 4.0 is a step backward. The 3.9 is so easy to work on.

 

[rover4x4]

keep the 3.9 front cover and use the 4.0 bottom end, its and easy swap

 

[hks3sgte]

I personally think going to the 4.0 is a step backward. The 3.9 is so easy to work on.

+1

 

[David Harris]

I personally think going to the 4.0 is a step backward. The 3.9 is so easy to work on.

Will second this. I've owned both and the 3.9 is much more simple and therefore easier to diagnose and fix, especially in the field. The 4.0 has some strengths, such as stronger cross-bolted main bearings and updated heads. However, a possible downside is that the later you get, the more liner and head gasket problems seem to arise, especially by 2000 or so. . . Whether this is tooling wearing out, or whatever, I don't know. . .

David

 

[atancreti]

Thank you to all the people that replied to this! I think that I will take my current 3.9 front cover and put it on the 4.0L. I agree with the 4.0 being a step backwards when it comes to head gaskets and electrical problems. I hope to avoid most of them with my 96 motor and putting the 95 front cover on it.