I picked up a rebuilt 3.9 V8 cheap from a local machine shop. It came out of a pre '95 D1 and has a distributor front cover. Somebody had had it rebuilt a couple of years ago and never paid for or came back for it.

I've had this machine shop do work for me before, so I trust them to have done a competent job.

I recently replaced a 4.6 Bosch engine that had a cracked cylinder, with a low mileage 4.0 GEMS (converting the 4.0 to the Bosch system). Things for the most part went smoothly, after swapping out the CPS, front cover, timing parts, etc... After a bit of tinkering it eventually ran well afterwards.

What troubles should I expect when installing the 3.9 into a 4.6 Bosch D2? All kinds of threads about going from 3.9 to 4.6, but not the other way around.

It looks like there's something about the 3.9 crankshaft being shorter and causing issues with using the 4.6 front cover, but I can't seem to find any definitive info about it being a dead end impossibility or if there is a work around.

I am aware there will probably be a noticeable power difference, but I figured I could very cheaply resurrect one of my dead Rovers from my parts parking lot... currently having four Rovers, with only one working right now...

I suppose I could just run the 3.9 with a distributor, but I imagine I would have transmission problems since it's computer controlled.

 

Okay, getting more creative with my search criteria yielded some forum posts on the topic.

Doesn't look good. Looks like there is no CPS spot or NOX spots.

May have to put it in my manual transmission D1...

 

If your manual transmission DI is GEMS, you'll have the same problem as with the DII. Even if your DI is 14CUX you'll still have minor issues to deal with if that 3.9L came out of a multi belt Rover (timing cover, cam shaft, ect).