The MGA With An Attitude
It looks to me like the intention of the design change is to place the pivot point in alignment with the horizontal arm of the lever to eliminate a cosine error in the mechanical motion. In other words, at the point where the needle valve closes the lever will be moving straight toward the needle rather than sweeping at an angle. This would eliminate a side load force on the needle, which may in turn reduce a tendency for the needle to stick when trying to close (see article CB-116A). It may be possible to reform (bend) the early lever to work with the later cover. You would need to make a very short offset "Z" bend right at the departure point from the "U" shape heel. Offset in the arm needs to be equal to the difference in height of the pivot points. End result should be having the "U" shape heel squared up and horizontal, then the offset bend, and then the next straight part of the lever also horizontal (at same height as the other arm). So how good are you at bending things? In the end you should be able to set height of both levers with a 7/16" diameter gauge pin (drill rod) per instructions in the Workshop Manual. On last check you can buy the AUD2285 lever from MGOC or Brown & Gammons in the UK. You might also buy it from TerrysJag.com or EnglishParts.com in the USA. |
Here is another problem that could cause fuel overflow or too-rich fuel mixture. For the MGA, original float covers were part numbers AUC4260 and AUC4261 for rear and front carburetors respectively. According to the Service Parts List there is a new part number for the front float cover, changing from AUC4261 to AUB2284. The change point is not noted, so this may be a change of replacement part rather than a production change. The difference in the later part is a taller stand for the float arm pivot shaft as shown above left.
This change of pivot height will mess up function of the valve lever. So along with the change of pivot height comes a new part number for the lever, changing from AUC198- to AUD2285. So if you buy a new front float cover, and it turns out to be the new style, then you also need to buy the matching valve lever to make it work. 
