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Here's my conversion from a petrol 2.25 to a 3.5. As I say to anyone else who asks this question - read lots and mentally walk through the job from start to finish a few times, making notes or a task list if you have to. Think about all the parts you will need and get them in advance. Nothing worse than a job coming to a stop because you need something tiny like a spigot bush!

http://www.v8forum.co.uk/forum/viewtopic.php?t=4483

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Here's my conversion from a petrol 2.25 to a 3.5. As I say to anyone else who asks this question - read lots and mentally walk through the job from start to finish a few times, making notes or a task list if you have to. Think about all the parts you will need and get them in advance. Nothing worse than a job coming to a stop because you need something tiny like a spigot bush!

http://www.v8forum.co.uk/forum/viewtopic.php?t=4483

Will look through it thanks! A 3.9 and a 4.0 won't be to far from this really will they both being rover v8's and yeah I need to make a list ideally of every part ill need so I can start buying them but I don't know where to start!

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Will look through it thanks! A 3.9 and a 4.0 won't be to far from this really will they both being rover v8's and yeah I need to make a list ideally of every part ill need so I can start buying them but I don't know where to start!

3.9 and 4.0 will be different as they never came with carbs, anything under about 20 years old will have fuel injection which is worth ~30bhp (see the table I posted) and better driveability. If you retain EFI it's worth looking at going to Megasquirt engine management as supplied by Nige (www.megasquirt-v8.co.uk) to give distributorless ignition (waterproof) and a host of other benefits.

P38 lumps (4.0 / 4.6) will have a different front end and ancillaries, as will later 3.9's.

My switch from old-style to new-style is here, as is a load of other V8 stuff in that thread. There's also some great V8 stuff from Nige and Bull Bar Cowboy in the technical archive.

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3.9 and 4.0 will be different as they never came with carbs, anything under about 20 years old will have fuel injection which is worth ~30bhp (see the table I posted) and better driveability. If you retain EFI it's worth looking at going to Megasquirt engine management as supplied by Nige (www.megasquirt-v8.co.uk) to give distributorless ignition (waterproof) and a host of other benefits.

P38 lumps (4.0 / 4.6) will have a different front end and ancillaries, as will later 3.9's.

My switch from old-style to new-style is here, as is a load of other V8 stuff in that thread. There's also some great V8 stuff from Nige and Bull Bar Cowboy in the technical archive.

I recently put a 3.9 in my Stage One. For various reasons, I chose not to use the modern bits - fuel injection, more modern timing cover with serpentine drive, air con, power steering, bigger alternator etc. What absolutely amazed me was that I could take all that stuff off and bolt the parts off my old 3.5 carb motor straight on. Basically the block just slid into the existing mounts, the exhaust manifold lined up, the old inlet manifold lined up, the old timing cover bolted straight on, the crank pulley fitted and lined up bang on. I just had to open up one hole in the alternator bracket as the 3.9 block was tapped for a bigger mounting bolt. I had to reset the carb needles a little and that was it. Fuel injection may well be worth 30bhp but it matters little. With carbs the 3.9 is very strong and super tractable. I had a fuel injected 3.5 Range Rover and this set up is definitely gruntier and super tractable. Magic off road and very modern on road.

That's not to say the newer parts aren't better, just that it's possible to keep a 3.9 very simple. Of course, if your goal is to use all your revs and power often, you wouldn't put carbs on (I suspect they would be a little too lean at full throttle). It's lovely that Land Rover kept the cross-range compatibility.

Don

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I disagree about the block problems with the bigger engines being overblown. I know of an awful lot of "disappointed" owners, even more so with the 4.6. Most of the problems are to do with porous blocks, shifted liners, or some sort of overheating problem. One thing causing another problem as it were.

Also, having to weigh out for top hat liners fitted is still EXPENSIVE. Fine and dandy for those lucky enough to have money falling out of their bottom, good luck to them. Same with Megasquirt etc. Great if you can afford it.

Sadly I cant.

I still maintain that a 3.5 is better for those on some sort of budget, AND more reliable. However, as has been rightly pointed out, the Defender spec engine should be avoided purely because of its low compression ratio, carb restrictors and points ignition (does anyone actually still HAVE points ignition ???)

Best bet would be 1986 onwards high comp engine on EFI for performance and "economy" but a carburettor engine will do fine.

The LT 85 IMO is not only stronger, but nicer to use as it has a nice positive change. If you do buy one, make sure it has the linkage for the transfer box with it, and also the LH mounting bracket, as these are really hard to find on their own. I quite fancy an auto though. I have got one of each........AND a TDI engine and box, but cant make up me mind which to use. Fuel prices being what they are and all

One thing I did forget though, is that the gearbox tunnel will need to be altered to the TD5 arrangement as it is physically bigger that an LT77/R380.

ALL the engines are getting on a bit now anyway, so you will be very lucky to be able to buy one and plonk it straight in, DESPITE what any seller might tell you ! I dont care what anyone says, I have seen enough of the insides of these engines, and rebuilt them (probably more that forty) and if it has done anything over 35k, you can bank on at least one of the camshaft lobes will be knackered. However its easily sorted, so dont let that put you off.

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I think the plan is to try pick up a 3.9 as it seems the easiest to put in I could still be persuaded to go with the 4 if I knew it would be just as easy but I don't know then hopefully get it on an engine stand and tinker with it in my free time while keepin an eye out for a lt85 then get them both together and whip them in!

If I was to choose the 4.0 over the 3.9 is it more complex to wire in? What is involved?

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3.9 will be "Hotwire" EFI, a bit of a spaghetti monster but quite basic. The 4.0 will be GEMS or Motronic and potentially not happy unless it thinks it's got a P38 connected to it, so quite a different beastie. Both are described in the RAVE manuals.

I've never bothered with either of them as I've been running Megasquirt on everything for about 10+ years now (3.5, 3.9 and 4.6).

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Ok maybe this will help you Tom

V8 engines and versions quick whizz through, plus and minus points ......

3.5

The original Rover V8, was a buick engine bough by BL and buggerred about with over decades, some BL additions were good, some hideous ...

The 3.5 comes in a few flavours

Car b or efi.

Forgetting the carb units the efi is one of the most horrible systems out there as is known as "Flapper", prob due

to the issues it will cause and you'll have a constant flap on getting it to behave.

There is NOTHING wrong with a good 3.5, and just BIN the flapper system and bolt a hotwire system to it

basically this is unbolt the inlet manifold from the block and lift off and replace.

There were are VERY few 3.5 Hotwires made, you'll be lucky to ever see one !

Good points - Rev well, and responsd well to tunning, cheap

Lower BHP means less BHP to wreck other stuff :D

You can find rebuilt units and they wioll be cheap .

Easy to get to run out of donor car..

if you get one a 3.9 cam works wonders in a 3.5 !

Bad points - same costs to do any rebuild(s) parts as any other V8 and the least BHP

now old, so beware that many are on last legs needing full rebuild.

V belts so lots of squeak

Truly vile Flapper EFI

The least amount of BHP

beware and check of recon / rebuild work done !

ECUs fail and are tricky now to repair

3.9

Finally a decent(ish) EFI "Hotwire"

2 main flavours

V Belt - same as the 3.5 is many ways, more BHP and Hotwire far far FAR better than Flapper ****

Its basically a 3.5 thats got a protien drink

Oh and better heads than 3.5s

Plus and minus as 3.5 except Hotwire is a PLUS !

And the serpentine 3.9

Better Oil pump as crank driven

No more squeaky belts

later ones also have extar bolts going from block into caps for strength called "Cross Bloted"

Same EFI - hotwire

Minus is that some of the ancillaries although better costs £s like alternators etc

again beware of moon miles motors, however its servicing and oil changes that make for a good V8 not miles

a low miles uncared for ANYTHING rover V8 will be a tea chest of poo

4.0

BL/ LR took the happy pills here and had a go at electronics - this will not be a easy engine to get running out of the donaor car.

BUT
The hardware on the engine - ie injectors etc are all hotwire, so you can put a Hotwire harness on it etc but its a lod of work

Pluses...erm hang on I am thinking ......no dizzy

Minuses.

GEMS efi will not be an easy get running

SPECUAL parts on timing cover - ie alternator waterpump, (do not ask me how I know :( ) these cost more and a re tricky to fine 2nd hand.

its not a 4 litre engine its the same cc as a 3.9 - LR "Marketing"

MANY are auto, you'll need a manual flywheel

ALL rover V8s take the same Mnaula flywheel from 3.5 onwards

4.2

A HUGELY overlooked engine

Pluses

More BHP, good grunt not as long stroke as a 4.6, few water probs

Hotwire so easy install and wire up

Std 3.9 V belt parts

Minus

Rare and fetch a premoum as are sort after

V belt sqeely belts

Non serpentine - so dizzy driven oil pump etc

4.6 GEMS

Think of it as a 4.0 with more BHP, less revvy and a aversion to getting hot

libner probs and overheating probs stuff of legend

A LONG stroke motor, so gruntly low down but doesn't really like being revved

4.6 THOR

Don't. - Just don't The end

......see : http://www.megasquirt-v8.co.uk/thor.php OK ? Don't !! same gfoes for the 4.0 THOR :lol:

There are lots of other minor bits and tweeks on the above engines, the above is a quick whizz through and is no way comprehensive..but just to finish

Stay away from SDI Rover car engines - Flapper

Stay away from early 10.5:1 P5 car engines with carbs, all sorts of reasosn

SUs if you have to are better than strombergs.

Don't even think of buying a Pulsair 90 V8 Engine, an asmatic mouse has more get up and go

ALL the engines 3.5 3.9 V and Serp 4.0 4.6 4.2 etc will ALL have same bellhousiong mountings, same engine mounting

hoes in block (but mounts themselves vary) all mounts can be swapped about

Twin exist manifolds (ie 2 holes on end of manifold and 2 x downpipes each side beat the early single pipe system big time

4.6 Exhaust headers are V good but crack in cold water (I KNOW this !)

and a good webshop for bits and info is : http://www.v8tuner.co.uk/ far more helpful than RIP... sorry RPI :blush: :ph34r:

I would still therefore recomend

3.9 V or Serp or 4.2 V as cheap and easy to fit with few probs and good power outputs.

Good 12 things for your V8 are :

  1. Composite Head gaskets to replace Tin, same for Valley Gasket
  2. Solid Timing Gear sets (standard stuff is poor!)
  3. ARP Head stud kit - beats Head bolts hands down
  4. Glue the sump on don't use a gasket STC50551 I think ?
  5. Rubber Rocker Cover gaskets not Cork
  6. DO NOT fit whizzy Camshafts - if you have to change the cam 3.9 std unit or a stump puller / torque cam
  7. VR1 Racing 20/50 mineral oil in ALL the above V8s
  8. If you buy a Cat engine change the tune resistor to non cat to switch to another programme in the ECU
  9. NGK BPR6ES Plugs
  10. Good leads - magnecor are the best
  11. Decent Air Box most 3.9 etc are too small, get a 90V8 or 110V8 one, or a def 300 TDi one !!
  12. 12. Oila nd filter changes REGUALRLY

Hope this helps.

Nige

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Huge quote removed ;)

3.9 it is mate thanks for all that ill keep my eyes peeled if I'm honest I don't care to much for chasing power figures I just want an easy v8 conversion that is manual and will run well with a lovely sound and enough grunt to do me off road that I'm sure any v8 has.

Next I need to find a rough step by step thread or a book or something I can follow in my head a few times before I begin buying parts does any oft know of a thread or a book I can buy or can anybody give me a quick step by step run through of what's involved

Edited by Happyoldgit
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  • 1 month later...

okay ive decided to go down the route of buying a donar car

im toying now between either the 4.0 older range rover

or a 3.9 disco manual

i want the manual box

if i was to get a manual 3.9 disco would the box be the lt85 that i need or will this box fit?

also one of the earlier commens stated that some engines are not easy to get running out of the donar but surely if i have the car there it would be a different story but then as the 4.0 rangey is auto and i want a manual im stuck again on making it be able to take the lt85 id also have to buy the lt85!

so basically my questuion is should i just get hold of a manul 3.9 disco and make my life a whole lot easier

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No, the Disco will have an R380.

Disco R380's have the gear shifter behind the transfer box lever, and in a defender this pops out close to/inside the seatbox. To fit the defender selector housing and put the gearstick into the normal defender position you need to either swap the selector shaft inside the box, or buy a wee adaptor piece from ashcrofts to allow you to fit the defender selector to the disco selector shaft.

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Why do you specifically want an LT85?

Defender (tdi) R380 would need some fiddling with to fit the V8, namely the spigot bearing on the TDI box is larger, so you'd have to machine the spigot on the engine out to the same size as the TDI shaft.

In your situation, your best bet is to buy something like the disco you linked, and drop the entire engine/box/transfer case into your defender.

Either swap the selector shaft, or buy the little adaptor piece (which saves you stripping the box down!), and fit a defender selector turret and your sorted.

Adaptor is here: http://www.ashcroft-transmissions.co.uk/index.php?act=viewProd&productId=375

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