Try a simple test: let your hot engine idle and check the temperature, then take the fan off and let it idle some more. See which overheats - with fan or without. That will tell you what difference the fan makes, even if it is marginal.
I’ve never had any overheating problems, either GT6 or Herald, with a good clean radiator and cooling system, although I do use the later plastic fan on my GT6 due to slight damage of the metal original.