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Hi, could you please advise on the merits of the metal 16 blade radiator fan on the mk1? Would it be better to replace with a cheaper plastic item from the usual suspects? Surely the lighter plastic fan would be better for the water pump bearing?

I like the 18 blade metal fan. I don't have overheating even on hot days in Australia (40C or +100F) and I've seen too many broken plastic fans to warn me from fitting one

I thrashed my 1100 Mini to Italy last year. Cooling set up was a recored Coventry radiator and a 16 blade fan. Only time it got a bit bothered was a slow grind up a very steep road on a hot day. After I removed the late mini splash guard things were better.

It makes a distinctive noise at motorway speeds and apparently the plastic fan is better for shifting air at speed.

I am no expert on fans but always thought the later plastic moulded fan was no doubt lighter and cheaper to produce but also quieter and more efficient at shifting air because the fan blades could be moulded to the optimum cross-section shape compared to the earlier flat metal fan blades.

'Cooperman' (a retired aeronautic Engineer) quoted this below in a "Metal Vs Plastic Fan?" thread on The Mini Forum some years ago:-
"The more blades you have the more likely you are to get 'cascade effect' at very high revs. This happens when the speed of the blades causes the fan to become, in effect, a solid disc (in fact, this effect is also known as 'disc-ing').
The plastic 11-blade fan seems good up to about 5000 rpm (engine speed and with the small water-pump/fan pulley).
For sustained high revs the 6-blade, or 'export' fan is excellent, as is the old competition 4-blade. Less blades seem to increase the engine noise.
Who can remember the early 16 blade steel fans which 'disced' at about 4500 rpm? Useless for any high-performance use."
https://www.theminiforum.co.uk/forums/t ... ?p=1566168

Just checked what David Vizard had to say about fans. He devotes about 3 paragraphs to it out of 500 odd pages in the big blue or yellow book, they are that important.
He had bit more to say in the 'How to Modify your Mini' book. But not a lot.
The 16 blade fan introduced in 1961 to reduce noise does the job, but it's definitely not a performance item. It saps more power than the alternatives, and as said above, at high revs it actually becomes less efficient. Clive Trickey suggested a cheap mod to this fan by cutting off opposing blades to reduce it to eight or four diametrically opposed blades. It would still do the job. But I could never see the point of this when you could stick a conventional two or four blade fan on in any case. You certainly wouldn't do this now.
DV said the eleven blade plastic fans (there were two different versions -12g2129 with 1.5" wide vanes and 12g1305 with 1" wide vanes ) were the most efficient in terms of shifting air versus power loss. He even suggested taking an equal amount off the length of each blade as it was actually too efficient on the small bore engines!
The four blade metal fan was effective but noisy. Two blades slightly less so.
The 6 blade 'export fan' may shift a lot of air but it also saps quite a lot of power. Again not a performance item. In a hot climate the export fan might make a marginal difference.
Vizard said the two blade metal fan was his weapon of choice for the factory belt driven set up. There's even a carbon fibre version available now.
For road use the efficiency of the fan is only really important at speeds of less than 30mph', particularly if stuck in slow moving traffic for any length of time, the electric fan on later models only becomes relevant in this scenario. Above 30mph and the air ram takes over. The side mounted rad location on the mini does of course necessitate some channelling of air to the rad by a fan, but the most important aspect in combating overheating is the size, position and type of radiator, not the fan.

I would only use the 16 blade fan if originality was important. For general use the plastic ones are fine, and if you don't mind the buzz the metal four blade is perfectly adequate. Personally I have used the metal two blade fan for years with no problems. The bonus is it makes changing the fan belt a doddle.
You pays your money and takes your choice.

I've tried them all and now have a modern plastic one with small pulley.

Can only speak as I find but the Minispares 11 blade plastic one works extremely well on my 1380 S

The way all fans work is the power needed to drive them is just about directly proportional to the volume of air moved. Some tweaks can be done to them to make them slightly more efficient or quieter, but they aren't going to make loads of differences, not enough to make a hot engine run cooler.