Although the cylinder heads look superficially 'the same' many changes have occurred since the introduction of the Rover SD1 back in 1976.  I intended to simply cover the latest 4.6 litre specification but due to recent interest you will find as comprehensive a guide to Rover V8 heads as you may hope to!

Pre 1976.  Although looking no different from the SD1 type heads, these utilized 12.7mm reach plugs and had smaller valves, both inlet and exhaust.

1976-87.  SD1 production for twin SUs (carbs in general), all V8s from the introduction of the SD1 took on the new specification cylinder heads.  They incorporated larger inlet & exhaust valves as well as revised combustion chambers (36cc), taking a 19mm reach spark plug.  Anything with a V8 between these dates should have this spec.

The EFI Vitesse  On introducing fuel injection a small cutout was ground in each inlet port to clear the injectors, as Efi was introduced with the Vitesse the heads also incorporated flowed valves, with a 30° back cut and wasted stems on the inlet valves, very different from the standard SD1 type and this was coupled with a more aggressive cam.

Early 90's.  Here comes the confusing time period.  It seems sure that all V8s now had Vitesse valves (but with out the cam or upgraded single springs).  In 93 or just before the valve guides changed to the modern cap type (blue), one for each valve, all V8s took on this feature yet the casting remained as per Vitesse.  4.2 Litre motors however also had factory standard heads, but during production Rover switched to composite gaskets, whilst retaining Vitesse-like heads and the heads were machined to bring back the required compression. The same thing happened to the then current 3.9; you may also see some 4.2s with only 10 head bolts, the outer 4 holes through the head being plugged, these are the composite gasket units.

Tempest and Thor.  With the introduction of the new Range Rover in 1994 a new head was brought into being, with a revised casting (No 2479) the head had larger ports than the Vitesse heads without the flowing and they retained the same valves and guides which were present from ~1993 onwards.  The combustion chamber volume (29cc) was also reduced (by simply machining off more material on the face) to compensate for the increased thickness of the composite head gaskets and probably most noticeable, the 14 head bolts were reduced to 10, the 4 outermost being removed.  In case you're told otherwise, 4.0 and 4.6 litre headsare identical.

Wildcat heads.  Supposedly these are the best heads available, if you want to go over 4.6 litres then the production head simply can't take the pace.  I'm my opinion they look a bit clunky...now a 32 valve conversion would be good, they are available for Chevy V8s.

Plus 8 Timing Covers

The Plus 8  V8 has been under our bonnets for so may years it is not surprising that many components have undergone changes, the timing cover or 'front cover' is one of the most noticeable.

Pre 1976  The cover uses rope oil seals around the front pulley and a short oil pump casing, the water pump is situated above and between the block water inlet passages, with the distributor held down with a clamp and separate bolt.

(N.B. Range Rover.  From it's introduction in 1970 this vehicle had a redesigned cover, the only differences from the saloon cover being the positioning of the larger water pump, above and to the left of the block water ways and an oil seal protector plate.)

From 1976 both of the covers gained deeper oil pump casings allowing for greater flow, metric oil filter threads and rubber lip seals for the pulley.

1987.  The SD1 ceased production and with it died the original saloon timing cover, from this date all covers were for 4x4 vehicles.

Post 1990.  The cover gained studs to hold in the distributor rather than a separate bolt.

1993.  A new cover was introduced for the 3.9 (and the non-Morgan 4.2) late model engines with long cranks, this is shown at the top of the page and was the best cover to date, using a rotor oil pump of greater capacity than the old type and using a new water pump design with a counter rotating impellor.  However it is not easy to fit to an older 3.5 as the crank nose was lengthened in order to accommodate the oil pump and pulley, 3.5 cranks aren't long enough.  Although the oil filter attaches and points in the same direction as the older cover, there is no separate oil pump base as obviously is is not required.

1994 - 1999  A new cover was introduced which was much thinner than it's forbearers, having no hole for a distributor the cover is very compact, having the oil filter fitting pointing directly downwards.  Again it isn't suitable for any V8 owner who wishes to run a distributor.

1999 - Present.  Identical except for an extra sender unit boss mounted above the oil filter housing.

N.B. It may be an idea to pick up a spare timing cover if you have a pre-1988.
 

Replacing Valve Seals or Valve Springs (with the heads on)

Valve stem seals can be replaced with the heads in place in the car. Bend up a 450mm piece of 10mm rod into a sharp vee, 50mm from one end. Then bend the rod at right angles next to the vee to form a handle.
The rod can be used to depress the valve spring by hooking the point of the vee over a rocker stud with a nut on it. To hold up  the valve, turn an old spark plug into an air connector and use a compressor, or feed about one metre of small rope into the cylinder and jam it up with the piston.