3.5 swap to 3.9 In my RRC

[Leo]

My original 3.5 has a horrific cam rattle and is now finally losing power ( i bought it with the rattle and drove it for 4 months before it really worsened)
I have a donor vehicle 1997 disco, the 3.9 runs beautifully. I have some fear of the sleeve slipping that you read about, but its a budget project and willing to take the chance, no idea of the mileage on the 3.9, but like i mentioned, it runs like butter....
My questions are: is it a direct swap? And should i expect a considerable improvement in power?
The RRC is a 1987....... The 3.5 barely dragged it around....i know it was sick, but just seems underpowered for the vehicle...( not trying to wind any body up, just sayin..)
I am a 6 out of 10 mechanic-wise, and am not afraid to do the swap on my own, it "feels" like a fairly staight foreward swap ( hey, stop laughing!) but any tips, warning, suggestions from experienced enthusiests would be greatly appreciated. I would be willing to pay to have the swap done if that appeals to anyone out there, the vehicles are in Kelowna right now, both driveable...not willing to spend more than 1000$ probably....and i have limited time, i have to do this from June 1-30 of this year.
Thanks for taking the tome to read this, and thanks in advance for your advice.
Cheers
Leo
P.S. At projects end, i will have the motorless disco (right now its running and everything works)and 3.5 for sale CHEAP! If you want to do the swap you get the parts truck and motor at a very special discount!

[Tony4921]

Hi, are you using the GEMS off the Discovery, or using the RRC distributor and carbs?

[red90]

It depends on how comfortable you are with swapping over all the electronics and getting them going on the new vehicle. You need to make sure every sensor is moved over and working. Earlier engines are a lot simpler.

[Leo]

They are both fuel injected...I think I will bring the electronics from the disco, the injector wires and overall condition are better...14 cux doesn't seem overly complicated Unless you have some "warnings" for me? I know the Lucas pretty well now, I've upgraded from the 13 to the 14, cleaned and rebuilt map sensors stepper motor, etc, etc...
I guess my main thoughts are around the serpentine vs v belt stuff....power steering pump pully ...
I think they should be pretty much identical block-motor mounts, exhaust manifolds, etc...?
Are they? Or is their any fabrication/clearance issues...that anyone knows is required?
Thanks again,
Leo

[red90]

A 97 Disco will have GEMS and not 14CUX. It is EFI and EDIS. It is not a big deal, but more complex and you need to make sure everything swaps over that talks to the ECU, not just the stuff attached to the engine. Some people get scared by engine management systems. If you are not one of those people, then there is nothing to worry about.

[Leo]

Thanks,
I might have the year wrong ( I live in Mexico 8 months of the year, the trucks aren't in front of me) i bought the disco parts truck just before I left a year ago....might be a 1995-6. My memory isn't what it used to be....:) but it is definitely a 3.9 with the 14cux. Same plenum chamber and map sensor, etc.
Thanks again for tips
Cheers
Leo

[Leo]

Really appreciate tips, but I think I better wait until I get both vehicles in front of me so I am not just speculating about all of the swap details....I am still looking for a mechanic to do the swap perhaps should the timing be right, so I guess that's my primary goal on this forum for now.
Thanks again,
Cheers
Leo
I'm sure I will have PLENTY of questions once I get into it myself! :drunken:

[bhoult]

I put a 3.9 in my 88 RRC to replace the 3.5. I essentially switched out the long block of the 3.9 for the 3.5. All of the 3.5 engine controls worked fine on the 3.9, so I wouldn't bother with "upgrading" the EFI unless the 13/14 era controls are already kaput. I did have to get a couple of used injectors to replace ones that weren't working on the 3.5 because it was so hashed - other than that it was all just a straight bolt across.

[Leo]

Ok, awesome, thanks. That gives me more confidence.
Did you notice an appreciable power improvement?
Cheers

[bhoult]

Ok, awesome, thanks. That gives me more confidence.
Did you notice an appreciable power improvement?
Cheers

night and day. The 3.5 was totally warn out so it had very little power. The 3.9 was a nice upgrade.

I also upgraded the cooling when I did the 3.9. I found a 93 in the bone yard and pulled the radiator and overflow assembly as well as the oil filter he assembly/cooling lines. That gave me the bigger radiator and improved engine/trans cooling capability.

I would go ahead and replace the timing chain and do the head gaskets when you swap out the engine. Also refresh the rear main seal while you're at it.

[Leo]

Ok, thanks again,
I'm looking for "night and day" for sure...:)
Nice to hear that comment. If I learn anything along the way (I'm sure I will!) I'll post. Such a great resource having these forums.
Cheers
Leo