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4,0 versus 3,9 V8


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In essence... they are a better engine, stronger mains, better oil pump, better cam chain arrangement, no dizzy, better heads.

Depending what you are sticking it in you may need to mod a few things, like a remote oil filter otherwise it can get bashed by the diff  :rolleyes: But it should all bolt up OK.

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The ECU wont be "keyed" to the engine.

An engine is a mechanical device, bits of metal, that go round and up and down.

The ECU may well be keyed to the vehicle immobiliser, and other electronic gubbins inside the car, but not the engine itself.

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Thor engines are significantly different to serpentine units, note not "Better" they have pros

and cons, I will sprout more when I have a mo, but often these engine don't have the handy "Seperate engine unplugable loom" that completely unplugs, which means you need to take care you get everything you need when removing it, be wary of removed engines "With everything there guv" as those bits missing can be ££££s to source

Nige

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Aragorn..

What I meant is you won’t get it to work without it and another ECU BCM etc from another P38 will have to be configured to work with it..

As Hybrid from hell says get the lot, if you’re going to do it.

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The other issue to consider is the later 4.0 blocks are nearly all timebombs, due to landrover using the best of the blocks for the 4.6's, and the carp leftover for the 4.0's

Not sure but i dont think the 3.9 or 4.2 blocks are quite as bad.

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I wouldn't even bother trying to unfangle the wiring, quicker & easier to Megasquirt it.

Not heard anything bad about the 4.0's, certainly not "time bombs", that was more the rep for the 4.6's and even then I think it's one of these rather overly alarmist reputations. Fundamentally it's an improvement on the 3.9.

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The "how to power tune rover v8" book by SpeedPro talks about the 4.0 blocks and says they have something like an 80% failure rate due to the block cracking into the water jacket.

The 4.6's fare much better because landrover scanned all the blocks and chose the ones with the best bore-to-waterjacket thickness to build 4.6's from, using the remainder (ie the worst ones) to build the 4.0's

http://books.google.co.uk/books?id=gmSavy1RPxEC&printsec=frontcover&dq=how+to+power+tune+rover+v8&source=bl&ots=nf6B7v5nsV&sig=dzY5cHHhrScRnUwySU7hRvfmosk&hl=en&ei=8ehFTMi1Oc-QsAaanbGSAQ&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCcQ6AEwBA#v=onepage&q&f=false

Theres an except from the book on there, Pages 25/26 mention the block thickness and the fact they build the 4.0's from the worst blocks, and on page 29 it talks about the failure rate, stating 80% for 4.0's and 15% for 4.6's.

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^^^

Correct, except one is blocks cracking and the other is dropped libners

having said that I am poss being pedantic, as either means your in deep f brown stuff

and the exact reason is different even thought the outcome is a fubared engine :rofl:

Rather than give my 'V8 Anorak' a big rustley outing, I'll pop it away as

its block / 4.0 wise / probs / pretty much covered now :P

:)

Nige

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HI All

And thank you wery mucho for the info, I gather that I should leave the 4.0 be.

But, and here is the next question and this might prove even more religios ?

Which Rover V8 would be the best choise ?

Its to be used in a car build for challenge events, and its to be Megasquirted

3.9 ?

4.2 ?

4.6 ?

OR Lexus 4.0 if I dare ask

Leaving out the 4.4 as I've been told that this beemer enginer is expensive to work with.

Cheers

Morten

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As you can see from my sig, i'm a bit of a fan of alternative v8's, however theres one thing you need to consider before looking at the lexus, audi or BMW options:

The rover has a fully sealed timing chest, whereas the Audi engine, and from what i can tell the lexus motor do not. The BMW-Range Rover engine may well have improved sealing compared with the car engine however i'm not sure. So for a challenge truck where your likely to be wading thru mud and water up to the windscreen, i'd be a bit wary of how the timing belt will handle it, if the casing gets full of silt etc.

The 3.5 engines are the most robust in terms of the block cracking/liner issues mentioned above, however the newer rover v8's (4.0 and 4.6) have much better oil pumps and as a result tend to be less worn out.

I think i'd try to get a 4.6.

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As you can see from my sig, i'm a bit of a fan of alternative v8's, however theres one thing you need to consider before looking at the lexus, audi or BMW options:

The rover has a fully sealed timing chest, whereas the Audi engine, and from what i can tell the lexus motor do not. The BMW-Range Rover engine may well have improved sealing compared with the car engine however i'm not sure. So for a challenge truck where your likely to be wading thru mud and water up to the windscreen, i'd be a bit wary of how the timing belt will handle it, if the casing gets full of silt etc.

The 3.5 engines are the most robust in terms of the block cracking/liner issues mentioned above, however the newer rover v8's (4.0 and 4.6) have much better oil pumps and as a result tend to be less worn out.

I think i'd try to get a 4.6.

Also usually Land Rover tweak any engines they borrow to improve oil delivery at extreme angles and a challenge truck will do extreme angles, so probably not good to get a non Land Rover engine.

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3.9 serp

Cross bolted block and generally good, look for gold colour inside the rocker

(remove drivers side before buying and look) aviod black and esp black cornflake looking

Next up I would still buy a 4.6 - more BHP and Torque, and get a good one (they are out there) and alls well.

I can't prove it, but in my experience the higher the spec of the RR it comes out of the better, seems to me

cooking versions of P38s had the worst lumps put in, so look for high end ones with service history, they still fail the MOTs

as there is so much to go wrong, just chose well, if its a runer ask to have it running and hold it at 3000 -3500 rpm for 10 mins

to check, and better still go drive it if it has any MOT left, check top hose and water levels before and after

Also Top hat linering sorts it all out for around £700, where as cracked block scrap, so a slipped liner is preferable IMHO to cracked block, and

why pore money into a 4.0 vs a 4.6 when you get so much more from 4.6

3.9s are a revvier engine, and a 3.9 with decent inlet work and trumpets and a few tweaks can be a screame for little money, non serp 3.9s are good too, the oil pump is deemed to

not be as good, but they can be had for peanuts £200-£300 for a superb one and have little issues as well

For megasquirting, 3.9 serp non serp or 4.6 would be my call, it then depends on what turns up, how much and the condition

forget the Gems loom, if MSing then either make ione or get a 3.9 loom and tweak

4.2 serp and 4.0 thors I would pass on unless bargain prices - my opinion and I am sure many may disagree

HTH

Nige

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How long is a piece of string?

I still think it's paranoia about the 4.0's, I've never heard anyone (Aaragon and his book excepted) say the 4.0 is to be avoided, and any which have made it this far through life you would hope would be reasonably OK. I'd always heard the 4.6 was the weakest what with it being bored & stroked, but then mine has been (touch wood) very well behaved up to now despite some terrible abuse. Bad news travels a lot further than good news. My other car is a 1.8 Freelander and that hasn't exploded and killed me yet either :P

3.5's are common as muck and cheap as chips, with MS'n'EDIS a fine solid choice on a budget.

3.9's give a useful increase in grunt without being expensive to buy.

4.2's give more torque again but are rarer and might not be best value.

4.0's and 4.6's are that much newer, have improved oil pumps and cross-bolted blocks, obviously more power/torque than the 3.5, the 4.6 having the most numbers and also therefore being the spendy one to buy. I've not looked at engine prices for some time so I've no idea how things stack up these days.

Any of them can be run with MS'n'EDIS very easily which makes life easy all round. Likewise the top end injection gubbins is interchangeable across the board.

Then you're into other factors - the 3.5, 3.9 & 4.2 lumps will all be longer in the tooth so you may want to budget a few quid for a rebuild, whereas a low-mileage P38 lump you may give it the benefit of the doubt. It's easy to throw the price of a used engine at rebuilding it by the time you've stuck a cam kit in, IMHO it's quite hard to justify spending much on bling bits (EG performance heads etc.) for a Rover 8 when you can either go up a size or buy a yank lump.

It really depends on your budget, what you want, and what it needs to do. The bargain basement option is to pull a 3.5 lump out of a crusty RRC for £150 and run it till it goes pop, the most ultimate numbers version is to splash out on a top-hat linered 4.6. In between, roll the dice and take your pick, there's not really a right answer.

As for other engines, I have looked several times at Jap/German/yank/whatever conversions but despite perceived benefits (more power, reliability, MPG, etc.) the way it stacks up by the time you've fitted it is that the ultimate gains are negligable - a 2-ton wardobe is never going to get great MPG, other engines make more power but it's quite hard to find anything with the low-end torque, reliability is a tricky one but RV8's plod on forever if looked after, and the parts, or even complete new engines, are cheap and plentiful, and an RV8 bolts in the hole with 100% genuine parts and no faffing.

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Hi All

Thank you very much for all the info and experience.

I think I go for a 3.9 Serp. As the 3.9's are easy to get at over here, but if a 4.6 turns up then that I will stop and have a look !

In what timeframe and in which cars did this engine go ?

Well i'll probably end up buying one in the UK as they are more plentyfull at you guys.

Se you all sometime between sunday and wednesday ! Going on a short roadtrip to the UK to pick some engines for a friend (Lexus -so what do you know :lol: )

Thanks Again for all this info.

Morten

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I run a Lexus 4.oltr in a comp motor on a zfhp22 4speed auto, replaced a supercharged 3.9 Rover with it over the winter. The Lexus is different animal!.

Rev,s well it just keeps going and even on the limit it never feels as if its going to let go! .Power well 260Bhp with no cat,s and more Torque than a 4.6 at about the same rpm.

Not an easy fit tho! lots of work on the bellhous,ing and had to make a sump to clear the diff on full bump travel.

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