Thread: Can i put a 3.5 into a 3.9 disco and what will i need

I'm not to sure on the legal issues of fitting an earlier motor into your Disco. Trying to get it to comply with ADR's could be hard however if it is running straight gas I think you can get around most of the pollution issues.

Why not sell the 3.5 to fund a 4.6 short motor? or another 3.9 short motor?

Disco dan, there wont be any problems with adr rules as i will fit the original 3.9 injection to the 3.5 therefor it will efectively be the same as the 3.9 emissions wise.

my biggest problem is will it fit and what do i have to swap and can it be done.

I also dont want to sell the 3.5 as its brand new and built tough, and if i can get it to fit in the disco it will be better as i can thrash the living daylights out of it and not worry about slipping liners in the 3.9s

No you cannot put the later oil pump front on an older motor.(without the later crank)

All Rover v8 blocks are BACKWARDS compatable, but its a big ask to have the designers of 1960 or so anticipate changes to the crank in 1993-4 and be FORWARDS compatable. (without a Delorean that is)
Regards Philip A

Originally Posted by PhilipA

... (without a Delorean that is)
Regards Philip A

and not even DeLorean anticipated the changes to it's DMC-12 in B2tF - they didn't even anticipate going broke!

Originally Posted by stage1V8109

Hi guys and girls,

Having my share of disco blues and over it... Here is the story.

I have a 3.9 injected, bog stock with 270 on the clock, 2 slipped liners ( compression test and the dredded hammering noises ) one pot fills up with water over night and uses oil like its going out of fashion. also presurises the cooling system.

Im pretty sure the engine is not worth a rebuild or if it is it wont be at this stage.. totaly rooted.. (blows smoke and gutless)

Any way i have a supurb warm built (very recent) 3.5 Natural aspirated engine that i built for my stage 1, with time and money being the big factor im looking at fitting this engine to my disco.

I have been told that i should fit a 3.9 cam and lifters to make the fuel injection right but not sure if i should being a warm build... what difference will it make ( it runs lpg 90% of the time)

my disco has a serpantine belt but the 3.5 has V belts, is it possible to run range rover power steering and air con?? is it a simple bolt off bolt on thing or is there engineering envolved.

intake and injection is no problem at all as i have all the gear on the old engine.

I have been told that i could convert the engine to serpantine belt but would run into problems with the oil pump drive and crank end...

is there any difference between a manual and auto crank? ie: will my flex plate bolt up to an engine that had an lt95 flywheel on it?

if anyone can help me with this i would be very thankful

and have i forgotten anything??



Regards Arty..

G`day Arty

Yes , bolt off on , some of the bolts that hold brackets in heads may be larger on the 3.9 and you will need all the belt adjusters/pulleys as well as all alternator brackets and other brackets ( alot of bits ).

If you have the entire pulley set up as well as the brackets and parts the pulleys go on for a 3.5 then it will work in the Disco .

If you can find an early 3.5 disco pulley set up in a manual it will show as they are V belt .

There are 3 or 4 versions of RR V belt set ups .

If you really want to run the serpintine belt on the 3.5 you can but you will need an engineering shop to extend the woodruff key slot in the nose of the crankshaft on the 3.5 and fit a longer key , this will drive the pump and Balancer/bottom pulley .

If you need the lenghth of the slot/key , i used to have it down somewhere but haven`t see it for awhile .

The 3.9 with the crank driven oil pump is the same length as a common 3.5 crank just the key is shorter on the 3.5 .
The 4.0/4.6Ltr cranks are around 20mm +- longer ( forget exactly but have it down somewhere )

You could fit the 3.9 crankshaft into the 3.5 and run serpy belt .

If you fit V belts , i`d suggest you remember that unless they all run true and are lined up properly they will give much trouble , fitted properly and true they are as good as anything .

If you run Petrol much the injection may need a little work but that will only be if you have bad economy and then 3.5 Discovery bits will interchange and if you run LPG mostly then won`t really matter what the injection does .

The bits for bolting the auto to the 3.5 are all bolt off and on as you put it .

Cheers

Why not get the v belts an pulleys and any other ancillaries you need from an early 3.9 disco (just prior to the updates) or a early 3.9 RR.

Garry

thanks for the help so far guys,

I managed to pick myself up a 91 disco with everything i need...
plus a full body lift kit, suspension lift, custom exhaust that i really like the note of too, for a VERY reasonable price, the only thing wrong with it is its maybe the worst for rust i have seen.... no worries to me

so all my V belt and injection worries are now taken care of as its a complete car.

Some more questions for you.

Will my 3.9 harness and ecu run the 3.5 ( ie: are they plug and play items ) or would i have to swap the looms and ecu from the 91 model into my 95.

The other thing is that this car is a 5 speed lt77s, im not clued up on the manuals as i have a ZF 4 speed auto which i quite like, but seeing as i have a complete donor vehicle, what are they like pros and cons???

also the fron prop shaft has been removed ( broken axel? transfer box? gearbox? ) any thoughts?

The engine is clean, runs great and loves to scream so it will sit in well under the hood.

And for anybody else wanting to ask the reason for me putting a 3.5 into a 3.9 car is im sick to death of porus blocks and bad liners, i have run 3.5's for years in many cars and flogged the backside out of them and NEVER had the issues i have had with 3.9's

Cheer again arty.