3.5 vs 3.9

[benbenukuk]

why is it that all the rrc I see for sale that have been used for off road are 3.5 and not the 3.9? Is the 3.5 better off road than the 3.9?  Ben

[denviks]

good question that is....ive just bought a 3.9 disco  

[clbarclay]

Cost and availability are probably the two most common reasons for using the 3.5 engine.


As for better off road, so I'm told the standard 3.5 exhaust is better protected around the gearbox cross member compared to the 3.9 exhaust, but thats about all I can think of that would be better.

The 3.5 isn't exactly lacking power/torque for general off road driving.

[Big Rich]

3.9 is a 3.5 bored out  

Rich

[hairyasswelder]

I would say it is down to cost. Last year a 3.9 would command at least £1000 - £1500 min. where a 3.5 about £600 - 900 for a reasonable runner.  The 3.5 is obviously the 'older model'

Maybe its the air suspension? Harder to modify??

Personally I prefer the 3.5 block as the 3.9 has its faults but the hotwire system is a hugh improvement over the flapper type EFI system.

Steve

[Bowie]

Air suspension was only from ~1992...

But my suspicions are that the electrics are a lot more complex, and more destined to go wrong on the later vehicles  :lol:

[Guardian.]

just had a new 3.9 in defender replacing the 3.5, and the 3.9 has heaps more power, totally different truck to drive now.
the 3.9 has my origional carbs fitted non of that efi stuff!

[Range Rover Blues]

On paper the 3.9 is about 15 BHP better IIRC.

A lot of that is down to the naughtier cam and bigger bore exhaust. particulary the downpipes.

Yes the 3.5 exhaust is less prone to damage as it goos above the gearbox crossmember, that said the crossmemebr is lower than the 3.9 exhaust.  Swings and roundabouts.  If you are worried then fit a 3.5 sports pie and manifold, that's what I've done :)

Hot wire is way better than flapper, I can't see why anyone would replace it with carbs.

3.9s are slightly more prone to block cracking because there is less metal round them, but the odds are it's not a problem.  Some have had it but then many havn't.  You could buy a S/H 3.9 for a few hunder quid now.

If you want an offroader pure and simple then whilst the air suspension is very capable the travel is limited and you can't fit longer shocks.

Spend a few hundred quid though and they can do this.

Another thing to remember is that all but the late 3.5s are visible hinge, I'm still looking for a decent set of doors.  The concealed hinge cars are easier to get spare panels for now and the doors gaps are closer, the whloe reason for the facelift was to get the RR sold in the USA.  The general build and spec of the car was focused on exports at this time, so a 3.9 had the new interior, better EFi (emissions, diagnostics etc) and better bodyshell.

A post '91 vogue should have more choice of interior colours, more toys (including EAS) but the same 3.9 engine, although with CATS.  The ignition timing is different so there is slightly less power.

The nicest of all bar the LSE was the autobiography model, available with the 4.2 engine but weighing less than a LSE.  The fastest showroom RRC made IFAIK.  Not one to trash off-road though [-X

[SebastianW]

But of course the timing on the newer ones can be changed to bring back that lost few horses couldnt it?

[Range Rover Blues]

I think the timing is altered because of the fuel mix, I'm not sure.  If you were that bothered then the ECU can be re-programmed by swapping one resitor in the wiring loom too.

But something in the back of my brain is telling me the reason Catalytic equiped cars had less advance is because 4 star was no-longer available and unleaded is 95 RON, about 3 star.

[FITZ4X4]

I've had about half a dozen 3.5's and two 3.9s my current off roader is a 3.9. The early 3.9s are the best as they dont have as many toys to go wrong. Mine is a 1989 with coventional springs no ABS, no AC. Basically it's the same as the 3.5 with a few more BHP. I do think the hot wire set up on the 3.9 is better than the 3.5 flapper type, other than that not a lot to choose between them. When the time comes to replace mine I will be looking for either a late 3.5 (88/89) or an early 3.9 (89/90) both would need to be autos without any toys.

[Range Rover Blues]

The good thing is most of the toys can be removed, like Meccano.  About the hardest to get rid os is ABS, though when it's working it's usefull.  I know a couple of people who RTV and ABS is allowed and therefore and advantage.

[FITZ4X4]

Yes ABS is useful but it's a [!Expletive Deleted!] when it plays up and lots of mud and water are a good recipe for mucking it up. There's is a guy at our club that RTV'd a classic with ABS it was a 1993 and it had traction control now that is useful :) but good help him when it all goes Tits up.