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MG MGB Technical - difference in 7-blade plastic fans

Moss sells two 7-blade plastic fans: 434-332 ('62-'71) and 434-340 ('72-'76).

What is the difference? The mounting hole pattern?

Tyler Irwin

Yes. RAY
rjm RAY

The early cars would not have had 7-blade fans at all. According to Clausager in "Original MGB" the 7-blade plastic fan was introduced on North American cars in December 1972. The earliest cars had a 3-blade metal fan, and this became a 6-blade metal fan on North American cars in 1967. The UK cars kept the 3-blade metal fan until March 1974.
Mike Howlett

From my reading of the Parts Catalogues the two 7-blade fans differed in that one was all-plastic and the other had metal inserts. At various times these were fitted to pumps GWP114, GWP117, GWP123 and GWP130 but both types were used with GWP117, implying the fixing holes were compatible.

Whilst originally the all-plastic was not used on North American cars until 1970, and was replaced by the metal-insert type in September 74, again the 3-blade metal and the all-plastic were used on pump GWP114, indicating that plastic could be used on early cars if more cooling is required.

I had a GT with a plastic fan, it sounded like Jumbo on reverse thrust. Binned it and stuck an electric fan on instead. Much, much quieter, more efficient blade design and it moves maximum air when you need it most, i.e., when stationary or crawling.
Allan Reeling

And Barney Gaylord has a few photos of modern plastic fans that shed their blades.
dominic clancy

And Barney Gaylord has a few photos of modern plastic fans that shed their blades.
dominic clancy

Hence the metal insert, I believe.

No, the metal inserts were there to stiffen the fan blades so that they would not stall out at elevated engine speeds as those of the earlier plastic fan would. The Moss Motors reproduction of the later fan does not have these steel inserts, but hopefully it is made of a stiffer material that makes such strengthening unnecessary.
Stephen Strange

Interesting. Aerofan manufactured a fan that was designed for the blades to flatten out as revs increased, to reduce losses (and noise).

The later plastic fan was of increased diameter and had staggered blades for noise reduction. The noisy earlier one was probably what Allen had. Small wonder that it was abandoned for a more efficient design. It's what I use on my engine.
Stephen Strange

After hitting a puddle after a heavy rainstorm and having the plastic fan blades curl outward and cut the bottom out of my radiator I banned them. Replaced with an electric fan. As Allan pointed out its much quieter now.
Richard Smith

This thread was discussed between 30/06/2016 and 10/07/2016

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