4.0 or 4.6 / Gems or Thor...Help, I'm confused

Hi,

New to the Land Rover scene and looking at buying a later P38 petrol (always wanted one for some strange reason).

Have been looking at various cars and was led to believe that the 4.0 was 'more reliable' than the 4.6. Also the later 'Thor' engine was better that the pre 98/99 ones.

Any advice on the subject would be greatly received.

Thanks
John

4 litre basically same engine different stroke a little less chance of cracking behind liner but is run on same ecu etc as 4.6, thor rather than gems apart from inlet same engine different ie bosch rather than lucas electrics

Hi mannerj,

I have a 4.6 Thor which is in my 2001 Vogue. I'm not sure there is any major reliability differences between the 4.0 and the 4.6 as they both can suffer from the same issues as far as I'm aware. Search for slipped liners / top hat repair, head gaskets, overheating, cracked blocks, porous blocks.

Overall the Thor appears to be a better package with Bosch engine management rather than Lucas for the earlier GEMS engines. The improved plenum of the Thor gives better torque and possible mpg though I suspect you'd need a microscope to find that one. Ultimate power is slightly down compared to the GEMS. Real world drivability is better for the Thor I think.

I've only briefly driven a 4.0 so cannot comment about its performance compared to my 4.6 Thor which is adequate. Expect 18mpg for mixed driving and early 20’s for motorway work. I’ve read that the 4.0 has similar mpg figures to that of the 4.6.
I’m happy with my Thor powered RR and from what I’ve read and my own experience it’s a better motor than the GEMS.

LW…..

mannerj said:

Hi,

New to the Land Rover scene and looking at buying a later P38 petrol (always wanted one for some strange reason).

Have been looking at various cars and was led to believe that the 4.0 was 'more reliable' than the 4.6. Also the later 'Thor' engine was better that the pre 98/99 ones.

Any advice on the subject would be greatly received.

Thanks
John

Click to expand...

I fitted a new 4.6 short block to my 4.0SE.....'the' only difference between the 4.0 and the 4.6 is stroke length....and the 4.6 is more economical.

Academic which one you fit as your ECU and current setup will welcome it gladly....
To protect your investment.....What I would recommend is to ensure your ECU is chipped to correct the standard Range Rover weak fuelling at mid range......Possibly the biggest single cause of slipped liners.....

As I mentioned above I bought a new short engine (4th engine) and used the existing heads (Skimmed and tested of course) RPI chip etc and it has been superb for the last 22k miles.....The chipping is also a good move if you go to LPG which I am in the middle of....

mannerj said:

Hi,

New to the Land Rover scene and looking at buying a later P38 petrol (always wanted one for some strange reason).

Have been looking at various cars and was led to believe that the 4.0 was 'more reliable' than the 4.6. Also the later 'Thor' engine was better that the pre 98/99 ones.

Any advice on the subject would be greatly received.

Thanks
John

Click to expand...

Apparently once LR became aware of the problem with the blocks, the 4.6s were given specially selected blocks which in theory ought to be more reliable. Not sure that's borne out in practice though. They both seem as bad/good as eachother in terms of block reliability. 4.6s have a stronger rear diff and a better (stronger) gearbox.

Not sure if Thor is any better than GEMS, but the airflow meters are cheaper for Thor. Alternators aren't though! Slightly more toys available on the later ones (but they probably won't work anyway).

Mammoth said:

I fitted a new 4.6 short block to my 4.0SE.....'the' only difference between the 4.0 and the 4.6 is stroke length....and the 4.6 is more economical.

Academic which one you fit as your ECU and current setup will welcome it gladly....
To protect your investment.....What I would recommend is to ensure your ECU is chipped to correct the standard Range Rover weak fuelling at mid range......Possibly the biggest single cause of slipped liners.....

As I mentioned above I bought a new short engine (4th engine) and used the existing heads (Skimmed and tested of course) RPI chip etc and it has been superb for the last 22k miles.....The chipping is also a good move if you go to LPG which I am in the middle of....

Click to expand...

Yet another one taken in by the RPI BS, the lean fuel map causing block cracking/loose liners.Its just a badly built engine taken beyond its reliable limit in terms of the amount of material supporting the liners.

thank god for that

After looking at the RPI Website the only thing they can offer for a Thor is new ignition leads. No chips & fish, nothing.

Hi All,

Thanks for the replies.

Just to summarise;

• the 4.0 is as bad as the 4.6
• the thor is probably better than the gems
• the blocks are cr@p
• rover burried their hends in the sand in the true tradition of British car makers
• these are not vehicle for people with deep pockets and short arms.

Better not show my other half this forum, she may change my mind for me..!!

Looking forward to this adventure......

John

mannerj said:

Hi All,

Thanks for the replies.

Just to summarise;

• the 4.0 is as bad as the 4.6

John

Click to expand...

Except the 4.6 has more power and slightly better economy.

Speaking from my own experience...

My 2000 4.6 had cracked block, found straight after I purchased, so I got a recon short replacement at no cost from the dealer. Tempting fate I know but... its run like a sewing machine for the last year ... eek...

Performace; driving through a local village last week loaded up on the way to the tip. Doing the 30mph limit, got an impatient new Disco 3 driver right up my backside... speed limit changes to 60 and he pulls out to overtake on a clear straight. I floor it in 3rd (as I have every right to), and he suddenly finds his spanking new D3 hasn't a cat in hells chance of getting past me and pulls back in. I usually have full respect to fellow LR drivers (except Gaylanders (only joking )), but didn't regret burning off that dhead D3.

eightinavee said:

Yet another one taken in by the RPI BS, the lean fuel map causing block cracking/loose liners.Its just a badly built engine taken beyond its reliable limit in terms of the amount of material supporting the liners.

Click to expand...

You may be absolutely correct but as one can only comment as a person 'taken in'....!! All I am capable of stating is that three engines went diddly donk....the fourth is purring along 4 years later.

Coincidence surely eh!

Mammoth said:

You may be absolutely correct but as one can only comment as a person 'taken in'....!! All I am capable of stating is that three engines went diddly donk....the fourth is purring along 4 years later.

Coincidence surely eh!

Click to expand...

Probably not,I'm just making the point that Gems or Bosch do not run a lean fuel map at cruise as RPI say - and its very easy to prove.
Single examples cant really be used,I must say I would have binned your car after the second engine !

eightinavee said:

I must say I would have binned your car after the second engine !

Click to expand...

Made me think. Cost of a P38 when new. Around 50 grand? Cost per year in maintenance plus repairs. Between 2 and 3 thousand a year. Over 15 years on average, maybe another 45k. So did they build a crappy car or did they build one we would fall in love with and spend all our cash on and they're laughing all the way to the bank? Love ain't blind, its just not good at math!

ok here is another theory as the porus block/slipped liner only happen to 3.9/4.0/4.2/4.6 what do all these engines have incoman? lambda sensors! non cat models do not suffer the same engine failure fate
gems stands for generic engine managment it thinks and learns and adpts to the engine compensating to wear
thor is the next level and is fully generic ecu

thus chips that are available for the gems do not make that much difference.
one of my customers has had one of my cruiser engines and a mark adams chip already fitted it is no quicker than the same engine without the chip!

on the thor engine it cannot be chipped and with happily adpt to all the mods you do to the engine

non cat 3.9 used to suffer same fate 3.5 efi the hot wire type never did surprisingly it has 200 thou thicker ali casting for liner to sit in with 3-4 thou interferrence fit,in the 90s we fitted alot in defenders and alot cracked as we proved by machining liners out,

I thort it were cos all the **** blocks were rebored 3.5's

GM knew years ago the liner were a risk!

well considering it was the 4.2 that started it off and it was just a stroked 3.9 and all had lambdase closed loop emissions which controls the emissions.
in the dealer all we ever saw was 4.2 we did one of the first and land rover took the whole engine away and supplyed a crate motor to replace it!
never did we see and 3.9 at the time

it was with the 3.9 that it started and lr said blocks were beefed up for wider liner ,we cut up several 3.9s and they wernt ,at that time they allways cracked on passenger side as the earlier water pumps had a bias to feed drivers side ,the later pump was thought would help,some blocks are obviously stronger than others no doubt down to are exacting build standards