The radiator fan of the original MGA was of metal construction. With time, lightweight plastic became the preferred material for later model MGB, 1973-1976. Considering that the earlier steel fans would occasionally fatigue and break throwing a blade (often with some collateral damage), the MG factory saw fit to produce a light plastic fan as a replacement part for the earlier MGB and MGA. Moss Motors is now making an accurate reproduction of that replacement plastic fan (picture).

Notice: This plastic fan is slightly larger diameter than the original steel fan. If you have a fan shroud installed, you may have to cut back the ID of the shroud to clear the tips of the plstic fan blade.

Original fan blade broken - - - Plastic replacement fan

The odd blade spacing on the plastic fan has method to the madness. This interrupts the otherwise regular resonance frequency of the air pulses to reduce fan noise. Better air foil shape of the molded plastic blades is also more efficient for producing more air flow. It may look a little quirky, and may not pass concours muster, as it was not original issue for MGA. It is however a period correct replacement part, for a period a few years after end of production of the car model.

More information at
www.mgaguru.com/tales/mobile24.htm#fan - Larger diameter, so trim the shroud.
www.mgaguru.com/tales/mobile29.htm#fan - Broken blades.

www.mgaguru.com/mgtech/faulty/ft080.htm - Faulty part report.
www.chicagolandmgclub.com/techtips/mgt/cooling.html - Blade design.
www.mgaguru.com/tales/mobile46.htm#bills - Broken blade.
www.mgaguru.com/tales/mobile48.htm#ncmgcc - Broken blade.

Installed May 6, 2015. Broken July 16, 2015 at 10,658 miles. New one installed August 15, 2015. Broken April 12, 2016 at 20,821 miles. Broken again May 13, 2016. Went back to steel fan blade. Apparenty these fans were made from the wrong type plastic. Some time within the next two years Moss had corrected the problem, and the plastic fans are now listed as "Nylon".

Please also see article CO-208 about 6-blade plastic fans.

Addendum, October 28, 2022:
Okay I got it. Look at the back side of the fan. The first faulty one has a single thin wall center hub. The later better one has a double wall hub with gusset dividers all around (much stronger).

The Moss nylon fan is 7-blade with asymmetrical spacing, so it runs quiet while moving more air than a standard steel fan (all good). I believe it is patterned after a later issue MGB nylon fan, so it may be larger diameter (slightly more than 10 inches). When I first installed one it touched the steel fan shroud I had been using since 1997, so I had to trim the shroud a bit for clearance. I don't know if this may be a problem with current issue plastic fan shrouds (or not).