A+ head castings - despite having the same 12G940 casting number - are considerably different in appearance, loosing the flat area behind the thermostat housing and around the rest of the rocker/head stud areas to a sculptured look - where these areas are replaced by a 'sunken' cast finish.

*Note:
The A+ castings were introduced with the appearance of the Metro in 1980, although some late 1275GTs (1979-on) had them fitted. Generally they are easily recognised by their colour - a putrid yellow on the small-bore castings and bright red on the large-bore ones, a paint finish that is VERY difficult to remove, even in a chemical tank.

The MG<p>See bottom for useful part numbers.</p>
<p>Now this may not be super-sonic speed-inducing power, it could just   as well be for maximum economy. In either case, it's the engines   volumetric efficiency (VE) under scrutiny - it's ability to breath in as   much correctly proportioned air/fuel  mix as possible in any given situation. Although the induction/exhaust system    plays an important part, there are effectively two major factors that dictate    performance increases - the camshaft and cylinder head. The induction and exhaust    elements (stage one kits, exhaust systems, etc.) and camshafts are covered in    various other articles in my 'Corner'. So here we'll have a look at cylinder  heads and dispel some of the myths and legends surrounding them.</p>

A+ heads generally have three collet grooves in the valves, collets are 14-degree cone taper instead of the 10-degree on single groove collets (so parts are not interchangeable between single and triple groove types) and the top-caps have a raised ridge around the collet hole.