Rover 4.6 Litre V8

I've recently rebuilt a 4.6 for my Land-Rover.  On this page you can follow the rebuild for yourself, along with gaining information on THE LAST in the line of Rover V8s.

Background to the 4.6 V8:    With increasing emission regulations in the late 80's predicted to continue for the foreseeable future, LR required a source of power for their flagship new Range Rover due for role out in mid 1994.  With no money to develop a clean sheet motor for the 4x4, the responsibility fell back on the original V8 engine.  To gain the power and prestige required for such a vehicle a motor with as much low end torque as possible combined with fuel efficiency was required.  The old 3.5 had many faults, which had been well documented over the years, and it must have seemed a good time to fix those said problems.  A 4.2 litre version had already been productionised for the old shape RR, sadly a tiny 10 BHP increase in power was seen from the older 3.9 litre unit introduced on Range Rovers in the late 80's, simply a bigger engine was required to propel the two tonne vehicle.  However Rover knew that the ultimate in reliability was also required, thus the old spec Rover engine required much improvement.  The 4.2 was actually a stop gap engine, introduced whilst the 4.6 was in the development stage at LR, thus they took the chance to introduce some of the new ideas into this engine, they included: Latest casting (not initial prod run) with provision for x-bolting and a new timing cover incorporating a crank driven oil pump with distributor and a cam retaining plate. 

When the 4.6 was introduced it included many features which added to its rigidity and reliability, the specification was as follows.

To compare the new and old take a look at the following photos:

The bottom end wasn't the only part to receive the full treatment, heads were reworked to increase flow by a claimed 5% and although inlet ports seem similar, exhaust ports are markedly increased in size.  Improvements:

Talking of gaskets they are all new too:

At the present time (2001) both the 4.0 and 4.6 litre V8s are manufactured by Rover in the West Midlands using as many identical parts as possible.  In fact the only palpable difference between the two is the crank, rods and pistons.  Heads are interchangeable, along with the blocks (2411) and timing covers all in the name of cost cutting.  On a materials track, the heads and blocks are cast in Yorkshire by VAW formally WYF (West Yorkshire Foundry), the heads being gravity die cast and the blocks a combination of die & sand casting (difficult bits with reentrant angles sand, less complex parts utilizing dies, cheers Andy & Gary).  Each block contains ~ £35 of aluminium LM25, which is the common or garden automotive alloy containing approximately 7.5% Silicon along with magnesium to enable a degree of solid solution strengthening.

Changes since introduction:    There haven't been too many of these but here is a few I know of:  The cam profile may have changed since 1994 (possibly in 1999) and so has the cam sprocket, with the cutouts becoming asymmetrical.  For the 1999 MY, Rover deleted the pressurized oil jets on the conrod big ends, to bring them in line with the 4.0 litre and reduce costs.  At the same time, and I can only put this down to a cost cutting program; the windage tray bolt holes were removed from the machining spec, so if your after a 4.6 unit to race with, source a pre 1999 unit.

Block Comparison - 76 SD1 3.5 vs 99 X-Bolted

Fueling the monster!

From 1994-99 both engines utilized the Lucas GEMS system recognizable by the large block sitting in the 'V', that was the plenum chamber & on all 4.0 and 4.6 it was painted black.  The system was far superior to the old shape Range-Rover type having full engine management including an rpm crank pickup, two anti knock sensors, the usual lambda sensors and four double ended coils.  For the 1999 model year the up rated 'thor' engine appeared with a huge aluminium tubular plenum and new management system from Bosch, the Monotronic with a full 'learning' capacity makes it difficult to convert to LPG.  The power figures were down for the 'thor' engine but torque improved, increasing acceleration and drivability, this modification was primarily to improve the low rpm response of the 4.0 litre rather than the 4.6; thanks Andy.

Links to pages concerned with the 4.6......be warned keep your wallet in a safe place!