should i go 4.6 ltr or stay with 3.9 ltr

[macbac]

Hi all

I am thinking of putting a 4.6 ltr in my 1990 RR as the 3.9 is getting verrry tied and i would like a little more power as i am going to be towing a off road trailer from now on. is this a good option and if so will it run of the 3.9s computer or will i need a 4.6 one. i am of course assuming it will just bolt strait in. allso will it hook up to my LPG system. is verry hard to start have to hold go peddle all the way to the floor to start and is consumming 30 ltr of fuel to a 100 kms. so is the 4.6 better or same on fuel any advise will be a great help.

Cheers

[Lucus]

4.6 all the way mate. The 14cux system will run the 4.6 without mod's but it will die in the ass in the top end.

My 4.6 averages 16 to 17ltrs per 100k's around town (im only pushing 31"s tho) and normally a couple of ltrs under that on the highway.(im running an aftermarket fuel injection system)

I personally would put the 4.6 in with a mild cam, some mild head work and a Tornado chip from the UK. You will need a crank spacer for the front of the crank to install 3.9 pulleys but this can easily be made from an old crank timing pulley

If you 3.9 is using 30ltr to the hundred i would get that looked at first. It must be running extremely rich to use that muc fuel and this will be costing you a lot of HP.

I'd suggest based on the hard starting and poor fuel consumption that you may have issues with your airflow meter and possibly fuel/coolant temp senders.

You'd want to get any issues sorted with the EFI system sorted first before fitting the new engine other wise you wont be happy with the end result

[macbac]

thank you for reply i run 35 off road and 33 on black. can i test air flow meter or does a mech have to do it and would it be better to use 4.6 computer as i am hopeing to run it with a surpantime belt.

cheers

[Lucus]

Running the 4.6 with the original computer requires a fair bit of work. You need a substantial amount of the original wiring and the BEM from the original car. If you cannot do this yourself it will cost you a ship load of dough.

there is heaps on info on here :
Range Rover Remedies (http://www.rangerovers.net/rremedies.htm#mafsensor)

and here:
RPi Engineering - V8 Engines (http://www.v8engines.com/carbs-2.htm)

scroll down for the info on testing the AFM

[macbac]

thanks again

whats BEM stand for. I all so plan on getting a half cut so that should have every thing i need but i might just start with the 14cux and see how it goes first. iam am old school mechanicly but electronics takes me a little while to get my head around.

[Lucus]

Body electronic module. The brain of the chassis. The Engine ecu goes looking for this as part of the immobilizer/security system.


The electronics aren't difficult. Its all about inputs and outputs:)

[trobbo]

it is a relatively simple conversion and all of your ancillaries can bolt straight onto a 4.6 short motor. you are probably much better off running an aftermarket ecu like a motec or wolf3d. You will be rid of your maf and be able to tune the fuel supply to match the 4.6 properly. The 14cux will run the 4.6 but only just and at the least it should be chipped. With a better fuel delivery provided by upgraded computer system you will be far happier with the result than that provided running a stock cmputer.

afaik the computer from the p38 rr will want to run a host of things other than just your fuel delivery.


oh yeah, forgot to mention. I have a 4.6 in my disco and am happy I did it.

[Traco]

4.6 for sure with 14CUX, high torque cam, Tornado Systems chip, Scorcher dissy...

[roverv8]

Whats the go with a 4.6,
Yes it's bigger but only 700cc bigger than the 3.9.

Why is the 3.9 so guttless on hills, they wind up quiet well,
But just seem to dye off on hills.
Well mine does anyway and the engine is resonably fresh,
Is it the cam in them???

[PhilipA]

The extra 15% torque in a 4.6 would really make a difference to the subjective hill climbing, so that is why people really love them.
Why is a 3.9 gutless?
1 The inlet length of a 3.9 is quite short as the inlet was designed for racing. This cuts down torque at low revs.
2 The 3.9 is tuned for 87 or so octane as the Oz spec is"rest of world" , while a 4.6 GEMS or Motronic has knock sensors so timing can be much more aggressive. This doesn't apply with retro fits of course

3 Land rover appear to reduce low rev torque to meet Oz Nox requirements.

My 3.9 with a Thor manifold , Unichip and head work produces 50% more "tractive effort" on a dyno at 2000RPM than a stock 3.9, and I would put forward considerably more than a 4.6.
Thor manifold =much longer=low torque but loss of some power at high revs
Unichip/Haltech piggyback= computer control odf timing=greatest gain.
Head work=another 7% in my case accross the board.

So you can make a 3.9 go well but it costs money and time but not 1/3 of what it would cost for a 4.6.
PS IMHO a standard cam is best. AND now with 190Kk on mine my cam is probably worn and timing retarded from chain stretch.LOL.
Regards Philip A

[macbac]

thanks all for youre help. would like to know more but 3.9 has done a lot of KM and would need a rebiuld and then to add all the bits PhilipA sugested would and i am only guessing would cost more than a low km 4.6 if any one has knoweledge on cost comparo i am all ears i have rebuilt a few Holden V8 in past and dont mind rebuilding the 3.9 if i can a cheive good gains at less cost but if the gain is not much great then 4.6 it would be easer just to drop in 4.6

Cheers

[PhilipA]

Yes I was thinking that later. if the 3.9 does not have good heads, timing cover , rocker shafts etc then maybe a second hand 4.6

But you have to be VERY careful that the one you get has good sleeves as 20% or more of 38A suffered sleeve slipping and cracked blocks.

I personally would not buy a used 4.6. Alternatively you could buy a known cracked block complete motor cheap and have it flange sleeved yourself, or buy a new block from Rpi .

Its not only the material , think of the labour cost if paying twice or the time if DIY.
Regards Philip A

[macbac]

sorry what is rpi iam only new to RR still learning the lingo but so far have Found RR have a lot of scope

[PhilipA]

"RPi Engineering - Specialised Rover Engines" (http://www.v8engines.com/)
Regards Philip A

[klappers]

Just did some light reading... It would appear that the cross sectional area of the "runner" appears to be more important than length.. More overall volume would appear to be more important then length.

[klappers]

Inlet Runner and Peak Torque Calculator (http://www.rbracing-rsr.com/runnertorquecalc.html)

[Lucus]

I have to agree with Phillip re the second hand 4.6 block. The only way i would purchase a secondhand block, known to be faulty for a very very competitive price (read FREE) by the time you spend the money to repair a faulty block your up around the cost of a new block.

FWIW When my 3.9 block **** the tin, I priced up flange liners and block machining and the cost to do that to the 3.9 was only a few hundred less than purchasing a new 4.6 short. Hence the decision to go to a 4.6

[PhilipA]

Mate , they are talking racing engines.

Maybe volume is a good measure but in the real world , intake length is the way it is achieved eg Falcon, BMW, Freelander V6, Mercedes and I am sure many others have variable length runners.( ie long for low down torque and short for high end power)

Do some reading on the Thor manifold and also look up "Hemholz resonance".

You may also do a search of old posts about Thor and have a look at the dyno curves I posted a couple of years ago.

Regards Philip A

[Traco]

I would advise you not to buy a new engine from RPI. The Coscast blocks they sell have started having problems with porous liners from some reports just like the LR ones did (see TVR, British V8, SD1 forums).

Instead I would strongly suggest you make sure any 94mm block you buy has had top hat liners fitted as this solves the problem entirely. TRS, Davis, Roverparts and a number of others can supply these locally for around $5k with crank and pistons fitted.

Or you could buy a used 4.6 for about $1,800 complete engine and get the block top hatted by a machine shop - it costs around $1,200.

[C H T]

I am going to use a Turner Engineering re-sleeved block - probably the best in the world. Ductile Iron liners, o-ring seals top and bottom, better machining than new genuine blocks, and very competively priced. Ex UK delivered in Aus at about $2500.00.

once you have driven a 4.6 Classic RR you won't want to go back to a 3.9

CHT

[Skiboy]

So CHT if I have a 3.9 with a slipped liner I could get a 4.6 from say Turner, add an after market computer, use the 3.9 injection and heads and ancillaries

What else do I need to have a strong 4.6

4.6 pistons/rings etc? Would I need different cam?

Or as the post earlier say are you better to buy a low km half cut 4.6 and then you are up for top hat liners to cover the water issue and an after market computer to deal with all the computer inputs. This second option sounds more straight forward and about the same cost as the first option.
Skiboy

[tempestv8]

Just curious - what sort of costs are involved in getting a 3.9 tophatted and fitted out with 4.6 crank and pistons?

In my case, my Disco II went from a 4.0 to a 4.6 and I was charged $8K for the privilege, since I have no engine skills. ;)

Definitely recommend it - my wife says the Disco is a far nicer drive and doesn't need to be constantly revved to 4,500 RPM when we are towing the campervan up some hils....

The inlet manifold now has a spacer and the top of the manifold now touches the sound insulation under the hood slightly.

Initial takeoff is much more lively and the engine seems to hold on to a higher gear for slightly longer, sometimes it crests some gentle hills without even downshifting whereas on the 4.0, a downshift was definitely required.

On Vapour Sequential Injection, urban driving, LPG consumption is 22 litres per 100 kms, so since the tank is only 62 litres usable, I get 280 kms between fills. On the highway, this goes to around 300 kms, so not much more but thankfully the vehicle does accelerate better.



edit: I should say that the cost also included a new water pump and radiator.... And a new set of rockers.

[macbac]

thanks all for youre input but i think i am more confused than be for LOL ether way u look at it nothing is strate forward? and cost out cum is ruffly the same also does the 3.9 have the same isue with sleeves droping.

Cheers

[PhilipA]

While the UK text books claim that 3.9 blocks have the same problem as 4.0-4.6 blocks AFAIK in Australia the 3.9s did not have the problem to the same degree as 4.0-4.6 mainly because of the installation.

3.9s were all in RRC and Disco 1 with 14CUX with a proven cross flow radiator design and an 88C thermostat.

Most 4.0-4.6 were initially in 38A Range Rovers which run hotter, and had the top of the radiator below the top radiator hose. Land Rover went through 5 top hose designs which apparently often failed and the cars overheated. So almost all early 38As experienced one or more overheats caused by failure of the top hose.

All things being equal, a new 4.6 run with a good cross flow radiator and 88C thermostat should be the same as a new 3.9 in reliability as they are the same bore .

Regards Philip A

[Lucus]

FWIW my 4.6 with a 93RRC cross flow rad, thermos and 88c thermo stat actually over cools on long down hill runs it often drops to 83/84 deg.

I personally think the New 4.6 blocks run cooler than the old 3.9 blocks due to the revised oiling system in them

[PhilipA]

Lucus, I think your thermostat is not fully closing.
Happened to me in Katoomba once when it was minus something and the bluddy engine went down to the cold and the enrichener came on.
When I changed the thermostat I founds the old one just stayed cracked open.
Regards Philip A

[Lucus]

Phillip,
I can head up greenmount hill here in Perth and the temp gets ups to 98/99 and one the way back down the temps drops to 84/85, I run overrun injection cut off so that has a bit to do with the rapid temp drop. The 4.6 definatly run cooler (with the right setup) than my old 3.9 did:)

[Traco]

Not so sure about the cooling system being the crux of the problem although it certainly didn't help on the P38s. The reason I say this is that quite a number of TVR Griffiths and Chimaeras (4.0, 4.3, 4.5 and 5.0 litre Rover V8 engines) have suffered the same fate and they utilise a non RR radiator and have the 14CUX injection system and LR distributor. And not all cases appear to have necessarily followed on from an overheating episode.

There are lots of theories around as to why and how the 94mm blocks go porous. Mark Adams believes the problem may be caused, or at least exacerbated, by the use of highly tightened stretch bolts.

Then again the incidence of slipped liners does seem to be significantly less with the old 3.9 blocks and these use stretch bolts too on the 1994-on engines.

[Traco]

I am going to use a Turner Engineering re-sleeved block - probably the best in the world. Ductile Iron liners, o-ring seals top and bottom, better machining than new genuine blocks, and very competively priced. Ex UK delivered in Aus at about $2500.00.

once you have driven a 4.6 Classic RR you won't want to go back to a 3.9

CHT

Agree they are the bench mark. Turner Engineering are a very professional outfit, a husband and wife team (Richard and Frida) with a couple of other employees. Established since 1979 they are now recognised as the market leader world-wide in the re-manufacture of Land Rover engines.

Their standards of engineering are very high. Their ductile iron flanged liners are the class of the field with a clever little seal that limits the chances of further problems. They have been used in supercharged 4.6 Rover drag racing engines that have pulled 8 sec quarters without nitrous
www.teamorange.org.uk

A lot of Turner's engines go to other suppliers of RV8s in the UK, and they do V8 performance heads specifically for Land Rovers which includes a very a nice job of smoothing the airflow into the inlet valves.

Their prices are reasonable. UKP3,400 for a new 4.6 long engine outright price, includes new pistons, pair of their performance heads, new rocker gear, new standard cam, lifters, pushrods and timing gears with all other gaskets and seals supplied for you to finish the build (front cover, rocker covers, etc).

They can build a long engine in 5 days and ship it to Aus within another 7 door to door and insured using DHL for UKP500. You then have to pay customs import duties at 10% of the AUD value then add GST (10% of the value + duty amount).

[DougLD]

Hi All
I am running a stroked 4.6 in the Rangie and getting around 16-18 liters per 100k and love it. Seems to run cool enough even when towing. I would probably go for a haltec instead of the gems engine management system if I were setting it up as this is the way it came when i bought it.
Regards
Doug