Fan balancer detail

Maybe everyone else has noticed this previously, but until now I had not noticed such a thing.
Take a look at this picture of the fan balancer pieces from an XK140engine…

The word BALANCER is stamped into each piece. Hopefully you can see it in this picture.
In a way, it makes sense to label various pieces, but on the other hand, why waste the time to label the two balancer pieces?
Careful attention seems to have been made by the factory to the balancing of the engine fan, for some reason.

I’m not aware of any other car from the XK period with removable balance weights on the cooling fan. Maybe Jaguar reasoned that the weights should be labeled to help prevent mechanics from removing them or not aligning them correctly with the tiny holes drilled in the hub.

Yes, balancing the fan is an important part of reducing engine noise, especially desirable on the saloons. My 120 and Mark V both have them. However the early 120s with the cast aluminum 5 blade fan did not.
Drawing more careful attention, notice the tiny little holes drilled in it. These matched identical holes in the original fan blade center spider.
If you put all this back so the holes all match, it may be close to balanced, if the blades haven’t been damaged.

So how do you balance a fan blade? I would think on bench top using a bubble level?

I used a tire balancing cone which has a bubble level.

Balancing the fan is mostly important for the water pump life expectancy.
Any vibrations from the fan will shortly destroy the water pump bearing.
I have had my fans balanced by an industrial tool balancing company.

You need a mandrel which is true, and the right diameter, and a set of bars or knife edges which are level and parallel.

Here’s a pic from the Mark 2 shop manual:

Here’s a thing sold by Harbor Freight and others, used for balancing motorcycle wheels, that could work with the right mandrel.

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Another option would be a simple lawn mower blade balancer, which costs less than $10. See eBay for examples. These are horizontal balancers so they would lend themselves to repositioning the original style style “balancer” weights to a different location on the spider to fine tune the balance.

However, lawn mower blade balancers can only handle a central hole up to about 1 3/8 inches in diameter. The central hole in our fan blades is over 2 inches in diameter. So some kind of adaptor would be needed.