|Posted on 10 July, 2014 at 20:40|
A bit more of Classic Range Rover facts and fables.
We have covered stopping, so let’s get into the going side of things.
The Range Rover being a 3.5ltr V8 to the 1990 models then 3.9ltr to the 1995 models, then a 4.6ltr option to date.
The most practical power increase option is to go to 4.6 litres. This can be achieved by either boring, sleeving and stroking a 3.5ltr block or stroking a 3.9ltr or replacing with a later 4.6 block.
The replacement 4.6ltr is the better option, as it is a much stronger block due to heavier webbing and cross bolting the main bearings. This is also a much better balanced engine than the earlier versions.
The existing 3.5 or 3.9 heads will bolt onto a 4.6 block using 4.6 gaskets. The camshaft is different in a 4.6 but the original can be transplanted whilst using the same front timing cover and distributor drive. I suggest a standard 3.9 auto camshaft.
The original engine can still be made to go quite well without huge changes but still lacks the low down torque necessary for auto or towing. Camshafts can be modified – compression raised and better induction and exhaust systems introduced. Camshafts were a problem on the earlier engines mainly because the engines were dirty – meaning that the oil was contaminated very quickly thus causing premature wear on the cam lobes due mainly to lack of sufficient oil changes or quality of oil.
If the fuel system of the earlier engines is being used on a 4.6 (i.e. Carburettors) there needs to be change of needles and resetting of mixtures. If the later fuel injected hotwire management system is being utilized, a modification or re-chip of the computer is necessary to get the mixtures rich enough under power.
Super charging a 3.5 or 3.9 is another good option and gives a good spread of extra horses throughout the range.
If you stick with the carburettor induction, then a replacement inlet manifold can be fitted to accept a spreadbore or four-barrel Carby to make the engine very responsive through the gears.
Intercoolers are great but a bit of a job on an Range Rover but getting fresh ambient air into the motor (via the air cleaner) is a good power booster alternative. Drawing hot engine bay air is a No No and should be avoided.
A snorkel or some device to direct the outside air into the air cleaner is a good thing. The addition of an electronic ignition to the pre 86 models is a big advantage. One can buy an aftermarket kit or fit a post 86 original distributor and ancillary gear.
The Auto Gearboxes cope well with the extra horsepower but the ZF Auto (86 and up) can be re-valved to get the torque converter lock up to come in later. This gives top gear much more flexibility, especially when towing.
An extra auto oil cooler is a must for towing.
The engine cooling system will need to be upgraded if you go to 4.6 litres. The radiator needs to be changed to the later core size for increased capacity and cooling area.
If the motor is fitted with a viscous fan hub it must be firm and operating to specs, otherwise a problem will arise with prolonged idling or slow running. The extra electronic fans must be operating correctly to help the engine fan in an emergency situation.
A good thing to be used a lot lately, especially in racing is to add an electric water pump, which is fitted into the lower radiator hose and helps to boost the flow of coolant through the radiator at crucial times via a thermo switch setup.
As you have gathered by now when you increase the horsepower you also increase the heat output and you have to get rid of it either via the coolant system or in other ways. A help in getting rid of some of the internal engine heat is to fit a good external oil cooler. Most English V8’s use a cooling coil in the radiator tank – this is OK for the UK, but Not for us here in OZ. Disconnect that cooler and run hoses to a good quality front mounted cooler – keeping the engine oil temperature down will lower the overall engine temperature quite substantially.
A successful cooling aid is to put vents on the rear side of the bonnet on Range Rovers to extract some of the hot air built up under the bonnet.
Ceramic coating of exhaust systems can also aid in heat transfer.
Good oil is important and most V8’s have lots of bearings and places that oil can escape and thus lose pressure when hot. The V8’s cope well on 25-50 grade Castrol Edgesport with Wynns friction additive and this combination gives very good pressure under heat and doesn’t lose its viscosity as quickly.
Leaking tappet covers are a nuisance in the Rover V8’s but if you fit the 4.6 Neoprene gaskets that will generally overcome the problem.
There are a lot of questions on fuel lately. The compression ratio will determine what grade of fuel must be used. Basically up to 9.1, run premium 95 unleaded, over that ratio, premium 98 unleaded must be used.
As a general rule in Rover V8’s you won’t need to put lead replacement additives into the fuel. Those motors have hard valve seats and get a fair amount of oil down the valve guides and this assists in lubricating the valves.
An option for fuel economy is to fit a diesel engine or LPG – I don’t like the noisy smelly things – more on that later.
End of Part Two – Until Next Time.
Dennis R Trigg. O.A.M. J.P. MIAME.