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What is the best v8


Dan88

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I took a tuned 300tdi out of my D90 and put a 3.9 high compresion engine in. result? dissapointment. I was expecting a 3.9 to leave the 300 tdi standing, it didnt. They use too much fuel and give very little power and i'm sorry but i dont believe anyone when they say a 3.5 RV8 makes a landy quick. (it might do compared to a siezed 2.5 NA diesel. I now have a 4.6 megasquirted engine in there, its been very reliable and has plenty of power and torque which makes me smile. IMHO if you are going to replace it then use the 4.6 or fit a tdi.

When this engine gives up i'm probably going to fit a Td5.

Steve

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What condition was the 3.9 in though? On paper the 3.9 should be the better engine, more torque and higher bhp...

From Parkers:

3.9 (Land Rover Discovery (89-98) 3.9 V8i 3d):

Engine Size 3947 cc

Cylinders 4

0-60 mph 10.5 s

Power Output 181 bhp

Valves 8 <- I do question this figure though!

Torque 313 Nm 230 lb-ft

300tdi (Land Rover Discovery (89-98) 300 Tdi 3d Auto):

Engine Size 2495 cc

Cylinders 4

0-60 mph 17.2 s

Power Output 111 bhp

Valves 8

Torque 265 Nm 195 lb-ft

*flame suit on* :ph34r:

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What condition was the 3.9 in though? On paper the 3.9 should be the better engine, more torque and higher bhp...

From Parkers:

3.9 (Land Rover Discovery (89-98) 3.9 V8i 3d):

Engine Size 3947 cc

Cylinders 4 0-60 mph 10.5 s

Power Output 181 bhp

Valves 8 <- I do question this figure though!

Torque 313 Nm 230 lb-ft

300tdi (Land Rover Discovery (89-98) 300 Tdi 3d Auto):

Engine Size 2495 cc

Cylinders 4

0-60 mph 17.2 s

Power Output 111 bhp

Valves 8

Torque 265 Nm 195 lb-ft

*flame suit on* :ph34r:

Best keep that suit on !!! :lol::blink:

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  • 4 weeks later...

ok proper anorak time for you guys here a few answers to help

3.5 bullet proof

3.9 pre cat bullet proof

3.9 / 4.2 with cats have porus blocks. 4.2 started it all off and was the first with cat and lambda sensor spec car that land rover offered in the uk

3.9/ 4.0 / 4.6 1995 onwards denoted as suffix b engine ten bolt heads comp gaskets and the serpentine drive belt system all with cats and lambdas

it is because of the lambdas that the engine's have problems they run lean at crusing speed to get a beter mpgs and ths causes high combustion temps which cause the block to crack and the linner to slip, as poor quality control of the casting process with very old and worn out casting machines too does not help!

people wanted better mpg but the ecu programers got it at a cost your engine

another theory to add which has also been spoke about is the porus issue due to electrical arking through the linner to the pistons could be due to poor engine earthing and weak anti freeze.

me personaly have a 4.6 best engine land rover ever made standard in a 90 it is a hoot in a classic or d2 it can be a monster! i'm building a 5.2 for my classic so will be intresting as iam going for a thicker linner set up

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Sorry Stuart - have to totally disagree,none of the closed loop v8's run lean at cruise,the only time they go lean if running properly is on overrun which is how it should be.Even the old 14Cux stuff will happily switch up rich with very little prodding,at cruise they are switching nicely.

More to do with carp quality control in machining and build,with too little metal supporting the liners.They should have stayed at 87.5mm bore - OR built a unit with wider bore centres.

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Just been reading Des Hammill's book on the Rover V8 - the first chapter or two goes through all the various flavours of block - it's interesting but also quite depressing reading - so many problems over the years.

Manufacturing had improved at this point and blocks were measured for wall thickness, one of the factors leading to block cracking was the cores slipped during casting leading to unequal thickness in the metal at either side of the cylinders. 4.6 engines were made from the best blocks BTW and if you find blue spots of paint on the block behind the pushrods (IIRC) then it's one of the best blocks, yellow and red being the other colours.

I think it's the other way around - red were the best blocks, reserved for the 4.6, yellow were intermediate and used on the 4.0 (and the 4.6 when they ran out of red blocks) and blue were the thinnest, 4.0 only.

Having given this a fair amount of thought over the years, if I had the money I'd go for a late Coscast 4.6 block (and if I was *really* rich, I'd get it top-hat linered for belts & braces) but failing that look for a cheap 4.0 or 4.6 and spend the money on getting it tested and sorted by an engineering shop. That way you have a degree of confidence that you're starting-out with something good. By going for a 4.0 or 4.6 you get the cross-bolted block and crank-driven oil pump, along with the serpentine belted front-end.

Moving away from the block, I'd also get one with the latter Bosch 'Thor' injection, assuming it's a 'normal' Land Rover and not a racer - the Thor manifold is (apparently & I'm hoping) much more torquey at lower revs at the expense of running out of puff at higher revs, which doesn't bother me. You can also (as I'm doing) retro-fit the Thor manifold to an earlier V8 but it's quite involved with lots of little 'gotchas' - once the engine's running, I'll write it up for the site.

Andrew.

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the Thor manifold is (apparently & I'm hoping) much more torquey at lower revs

Depends, I think the figure is +20 lb/ft max over the old version, worth having but not world-changing.

I found Des Hammill to all be a little behind the times really, quite noticable that the original books were about twice as thick as the revised versions, and as with most tuning stuff it's not always in-line with what you want/need from an engine in a big heavy 4x4.

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Depends, I think the figure is +20 lb/ft max over the old version, worth having but not world-changing.

That sounds about right, I had the 20 lbft number in my head but couldn't remember from where. I'm hoping this quote from mez.co.uk will be accurate:

"The Thor manifold, when used with either a standard cam or a mildly tuned cam, gives a strong torque peak at around 2,000 rpm, much higher than that achievable with the Lucas plenum design."

If it's true that should be ideal for long-distance driving as 2,000rpm is about 65mph in 5th in the 110. The old Lucas 14CUX on the 3.9 with the standard cam struggled a bit with this, particularly when the 110 was in 'family holiday fully laden mode', fine on the flat but give it a slight hill or headwind and the engine really started to labour.

I found Des Hammill to all be a little behind the times really, quite noticable that the original books were about twice as thick as the revised versions, and as with most tuning stuff it's not always in-line with what you want/need from an engine in a big heavy 4x4.

True, particularly about the tuning stuff (and the advertorial chapters for JE and Wildcat are worth skipping) but it's a handy reference for the RV8 upto the GEMS 4.6. Certainly more use than the David Hardcastle book, which stops at the 4.2, although the pictures are fun :)

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Having run 3.5,3.9 and 4.2, all on LPG, and never had any problems with any of them, I'd give my vote to the 4.2, with oil changes at most every 5000 miles, and a constant eye on the temperature guage!

Perhaps I've just been lucky, but in twenty odd years, and inter-galactic mileage, I've not had an engine fail yet!

Should it ever happen though, Stuart will fix it!

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I think it's the other way around - red were the best blocks, reserved for the 4.6, yellow were intermediate and used on the 4.0 (and the 4.6 when they ran out of red blocks) and blue were the thinnest, 4.0 only.

Andrew.

Well it's a long while since I read it (and I think I leant it someone so don't have a copy now). I also remember something about the liners often being oit of place, again going off memory weren't they cast in place?

Now as for thicker liners, the 4.2 uses the "Iceberg" crank, intended to give a 3.5 V8 engine with Diesel heads. How think must the liners have been to reduce 4275 to 3500?

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Well it's a long while since I read it (and I think I leant it someone so don't have a copy now). I also remember something about the liners often being oit of place, again going off memory weren't they cast in place?

Have to be very careful in what I post here as my knowledge is totally outclassed by you guys :o but I think you'll find that it was the yanks that cast the liners in the original 215 ci block & Rover who went for the press-in method. GM one / Rover nil, or am I talking out of my backside?

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No you're right there, one of the criticisms of the rover V8 is that the liners weren't pressed home fully, should have rememebred that.

The reason i referred to it was I recall from an article that the V8 was criticised for the liners being out of place, which becomes evident when the liners are machined out of the block.

Anyway, better start going to bed earlier as I'm obvioulsy not thinking straight.

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all the engines i have done have been cat/lambda set up engines even more so with the p38a engine which has a set parmeter of achiving 14-1 ratio when cruising.

non cat engines are more reliable than a lambda spec engine every time.

it was the 4.2 that started the porus issue not slipped liner's, slipped liners are because the block has cracked and allowed the block to expand causing the linner to shift thus chomping its way though the head gasket.

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it was the 4.2 that started the porus issue not slipped liner's, slipped liners are because the block has cracked and allowed the block to expand causing the linner to shift thus chomping its way though the head gasket.

That's always been my understanding, so how do the acclaimed 'top-hat liner' blocks avoid the original cracking problem?

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They don't, other than the liner is held in place by the top hat rather than being a tight fit.

My understanding is that "porous block syndrome" was caused by cracks behind the liner, not a casting that looks like an Aero. After all the head gasket sela to the top of the liner so in theory the block could be perforated.

One throry I've heard is that about 3 instances of overheating causes enough stress for the casting to fail in the area where the bore meets the top deck.

I've also heard that later gearboxs (and the 4.6 gearbox) being set up to hold higher gears lead to excessive differential heating from the top to the bottom of the liner (high throttle opening/low revs) but don't know if there is evidence to support that.

As for the 4.2, well there does eem to have been a spate of them getting new engines at around 100,000 miles, certainly for the relatively low numbers made.

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[quote name='Range Rover Blues' timestamp='1299624468' post='569697'

I've also heard that later gearboxs (and the 4.6 gearbox) being set up to hold higher gears lead to excessive differential heating from the top to the bottom of the liner (high throttle opening/low revs) but don't know if there is evidence to support that.

As for the 4.2, well there does eem to have been a spate of them getting new engines at around 100,000 miles, certainly for the relatively low numbers made.

RPI's theory is that the extra torque of the 4.6 makes it less likely to kick-down whilst pulling hard, thereby leading to the same senario. When my own 3.9 slipped a liner in '02 I did a lot of research on the subject, it appears that early 4.6's were slipping liners for a hobby & causing main stealers a shed load of headaches as LR was still in denial mode.

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Sorry, haven´t read the thread. So in case I double-post sth., please ignore.

So this is a "cut" through the cylinder walls of a standard rover block. The piston would be in the middle.

Blue = coolant passage. Grey = block, aluminium. Red = liner. Green = Head gasket

Schema-ohne-flanschbuchse.PNG

The head gasket does not seal to the liner.

That is why coolant can pass the gasket and leak into the cylinder (or combustion gases opposite way into the cooling system).

Now this is: Yellow = Coolant that gets into the cylinder (when the engine just been switched off. While running I´ll expect the combustion gases to be under higher pressure and force their way forward, pressurizing the coolant.

Schema-ohne-flanschbuchse-crack.JPG

And this is, how a T-liner seals. No way for any contact/bypass between gases and coolant.

Schema-mit-flanschbuchse.PNG

I think we had a discussion in the megasquirt thread about the mixtures. I really doubt that the vehicles, the newer ones moreso, will be allowed to disregard the 14.7:1 stochiometric point for the cats dealing best with the exhaust gases. Unless at full throttle.

The narrow band sonds used are ONLY usefull to tell you the 14.7 turn-point. 14.1:1 will be seen as "rich" regardless of being 12.5:1 rich or 14:5:1 rich. How the hell will the Ecu be able to close-loop controll the mixture to 14.1:1 then. I am not 100% sure the P38 uses wideband sonds, which would allow to precisely detect a mixture of 14.1:1 or whatever. Nevertheless theses vehicles are subject to emissions >>> I´ll bet they run at 14.7:1.

There is one aspect, not much considered - the thermostat opening temperatures. The P38 run much hotter, than the EFI-RRC, and these in turn run hotter than the 3.5 carbed models. Higher block temperatures were necessary for emission reasons (IIRC), but result in higher stresses due to metal expansion issues of aluminium and steel. Additionally the 4.6 simply has more displacement to fill with fuel and air > therefore under high load it will put out more heat when the mixture burns - while the cooling system is the same of the "smaller" engines.

After all, I stopped believing the RPI-theory. Rover obviously thought casting imperfections were the cause of the cracked block. The latest consequence of that instant is the coscast-production of the Block (by Mahle). That shall make sure the coolant passage between two cylinders is centric between them and the wall thickness behind the cylinder liners is of the same minimum thickness all over. Google told me that even coscast blocks are in the workshops. Making the mixtures richer at cruise will do more harm than making it leaner - in terms of combustion temperatures, just as you get less heat from a campfire if you put less logs on it. 14.1:1 is where the combustion is hottest (which needn´t equal to being the most "amount" of heat - as you can have that mixture at idle, with very little air and fuel and a richer and cooler mixture at full throttle wich expells more heat.

So to my believing the answer to the cracked block is neither a new block nor Tornado Chips, but only T-liners.

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Hi guys,

I have been wondering something while reading this thread. I have a 1993 3.9EFI with lambda sensors in my RRC & also a spare 3.9EFI pre cat engine out of a 1991 RRC, I was going to sell the 91 pre cat 3.9 until somebody told me that the 3.9V8 goes porous so thought maybe I should hold on to it as a spare just in case?

This might be a stupid Question but will it make any difference if I fit the pre cat engine if I ever had to swap it over, I would still use the lambda sensors as they are there on the loom but I have removed the cats & it runs on LPG? I've been told that it will get through an MOT as long as I do the emissions test on LPG. I've just fitted a set of performance manifolds with no cats on it & had to weld in the lambda sensor bosses, do I need them though?

Also from what I've been reading, is the pre cat engine better then?

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Hi guys,

I have been wondering something while reading this thread. I have a 1993 3.9EFI with lambda sensors in my RRC & also a spare 3.9EFI pre cat engine out of a 1991 RRC, I was going to sell the 91 pre cat 3.9 until somebody told me that the 3.9V8 goes porous so thought maybe I should hold on to it as a spare just in case?

This might be a stupid Question but will it make any difference if I fit the pre cat engine if I ever had to swap it over, I would still use the lambda sensors as they are there on the loom but I have removed the cats & it runs on LPG? I've been told that it will get through an MOT as long as I do the emissions test on LPG. I've just fitted a set of performance manifolds with no cats on it & had to weld in the lambda sensor bosses, do I need them though?

Also from what I've been reading, is the pre cat engine better then?

Well, just take my post as a point of view. Quite often, I experienced, it is contrary to others. But each has to go his/her´s own paths. I might add that I far from being an engineer by profession. I say so because we take the written word for granted, usually. So just listen to the arguments and make your own thoughts. With my posts and that of others. (Amen. :) ).

Ok, back to topic. AFAICS it doesn´t matter which engine you take. As long as they are both 3.9l. Whether you use lambda sonds depends on the ECU. IF the ECU is set up to work with them, they will miss them if you omit them. If the ECU does not expect lambda signals, it makes no difference if they are there or not. The MY of ECUs that you drive can be set up by a simpe resistor next to the ECU in the wiring loom (IIRC). So use lambda sensors if you want to, but then tell the Ecu (by putting in the correct resistor) to count on them. If you drive with Lambda sensors, but do not connect them to the ECU, there are chances they get damaged. That you don´t have cats neither bothers the engine nor the ECU, but only the MOT and emission test. If you manage to fool the test by means of LPG, ok then.

Usually we, over here, do not have a choice about using lambdas or not. Maybe regulations and MOT-men are less strict overseas. In my country you are more than likely to fail the MOT without cats, because the MOT-man , counting 1+1, will know that the car will not comply with the law and cannot honestly fulfill the regulations. Unless the car is much older than yours.

I am not quite sure, that the non-cat engines are less susceptible to the crack-problem. The 3.5l certainly is, because the less of cylinder bore leaves more aluminium behind the liners. But as soon as the bore is 94.00mm, the problem arises. I follow that topic for quite a while, but have not yet understood what the "porous" does mean. People who, for my reading, understand a thing about casting, do not confirm that the block casting is porous in a kind of a sponge. It is due to the "too little" aluminium behind the liners to withstand the thermal and whichever stresses > then the thin aluminium wall cracks and water can make it´s way. This happens at higher mileage usually. Not within the first 50k miles.

It is not granted that another 3.9 is better than the other. There are many that reach high mileages. But there are also some which replace a faulty item and the driver happens to realize that the replacement suffers the same fault. I do not run a workshop, I only follow the topic closely. And the cracks appear with all 3.9, being cat or non cat, and 4.0,4.2,4.6. I could imagine that the non-cat 3.9 seem to be less of a problem just because the cat-versions were produced in much higher numbers, so a objectve comparison is not easy.

I´d say in your case it depends on what you have in mind with the car. If it needs to be kept in shape with least possible effort and costs, then you should keep the spare engine of which you know it is good. If you have plans to keep the car for a long while you could as well drive as long as it goes, and in case of a crack with water consumption send the block to Turner (or sbd else) to have T-liners put in.

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That you don´t have cats neither bothers the engine nor the ECU, but only the MOT and emission test. If you manage to fool the test by means of LPG, ok then.

In the UK, if a vehicle is presented for testing on LPG, the emmisions standards it is required to meet is the same as the pre-Cat test, so pretty lenient :)

So it's not really 'fooling' the system, but recognising that LPG'd vehicles with aftermarket ECUs or no ECU at all is never going to be as good as a fully developed Petrol EFI ECU on a produciton car :)

If you are all so worried about your V8, go fit a diesel, personally I am just going to drive it and drive it and drive it :)

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