Rover 800 – M and T Cylinder heads

Note from James Copp-Taylor:-

Another from my archives, actually found on my old website, via ‘Wayback machine’. The photos have long since vanished, but, hopefully the text should be enough to describe the numerous differences between the M and T series cylinders, used on 2.0 Rover 800s. The T series head was found on the Mk2, from around October 1991. The M series, the 820 from 1986. Certain R8 2 and 400 series vehicles also used the M and T series engines.

In stripping the M series and T series heads I have noticed a number of differences and modifications that have been implemented to improve on the design and fix some problems with the M16 head. One noticable area is the camshafts, which have changed slightly, on the T series they no longer contain a grove a carry oil, the oil hole supplying them is larger, presumably enabling a greater amount of lubrication and helping to prevent premature cam failure, observe the two camshafts opposite, the lower one is off the M16, the top one off the T series, notice how there are oil ways cut into the M series cam. Timings on the T series cam are also different to suit the catalysed nature of the engine.

The entire head casting is different to the M16, this is the T16 to the left. The plug trumpets are now part of the overall head design and the previously unoccupied area in the centre of the head is now used by the oil, this design feature has a number of advantages over the M series design. I can theorize that with more oil flowing over this part of the head, right above the combustion chambers, will allow heat to be transferred with far greater efficiency than before, this will lower the temperature the valves are forced to work under and therefore stop the exhaust valves from burning out, a good idea which could work very well, it also give for better top end lubrication and may have a lot to do with the PCV that is now contained within the head itself.

Take a look at the valves, the one on the left is a T series exhaust valve, the one on the right, an M series valve. Notice how the T series valve is tapered out at the bottom, this means they are not interchangeable, as I discovered much to my annoyance. The slight tapering on the T series valve does lead to an annoying design fault on the T series engine, it isn’t unknown for valves to stick, the curve provides ample growth area for deposits such as carbon, gum type stuff and other little nasties, a good blast with some Redex may help the issue but usually dismantling and cleaning off is the only remedy.