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MG MGB Technical - Engine fan blade numbers

HI ALL.
I have a 5 bearing 1800 engine in my MGA.
I want to put a new engine fan on and I see that there are various fans with varying numbers of blades. Do they make a difference, my A does like to run a little hot in traffic so want the best fan to fit. I don't want to go electric.
Any help appreciated.
Regards. Simon
s page

Have a look at Paul's site. - http://www.mgb-stuff.org.uk/coolingtext.htm#mfans
Nigel Atkins

Hi Nigel,
Many thanks.
Great info, I will get my tape measuring tape out.
Regards. Simon
s page

Simon,
I was just a signpost, Paul done all the work. Bear in mind the B engine bay is different, more open, than the A.

I'm a big fan (pun intended) of prevention, of heat building in this case, and use (a one-time) simple but thorough cleaning method of the whole cooling/heating system. Email me if you want a (MS Word) copy.
Nigel Atkins

Just in case you're not aware-
Moss now do a 7 blade plastic fan with the correct offset etc as a direct replacement for the MGA-MGB metal fan
Part No.-434-332

https://mossmotors.com/fan-7-blade-plastic-replacement-for-metal-fan

willy
William Revit

I hope they have improved the centre location. The centre hole, which should spigot on the pump boss, had quite a bit of clearance, making accurate location and balance difficult
Paul Walbran

Does it use grommets and spacers like the original? It's those that provide the centring, on CB at least.
paulh4

I've only fitted one so far Paul and as PW says the hole is quite large, The one I got didn't have any metal support in the bolt holes so I took it that it took the grommets but the mounting holes had to be opened out a little to the metal fan hole size to get it to take the grommets properly---You can notice the extra airflow at idle so should be good in the traffic on hot days, revving the engine doesn't make any more noise than normal, you can hear the fan sing a tiny little bit at high revs but it's not at all an annoying sound---nothing at normal road speed just at higher speed/revs
William Revit

Moss Europe show a similar fan with adapter for 18V engines 71-76 https://www.moss-europe.co.uk/cooling-fan-assembly-7-blade-ahh6999k.html?assoc=711363. Showing as on back order, but the fan itself seems to be available showing as 'useable on MGB 1962-70'.

The difference dates to the change from 18G to 18V and a different pump so it depends which 5-brg Simon has.
paulh4

Hi. All. It's an 18V engine. Moss at Stockport have the fan and are holding it for me. Its just the fan, I hope it should just replace the metal 4 blade.


s page

Hi ALL.
Bought the fan but it won't fit over the waterpump pully. I see the the kit does come with a spacer,(nca)
Are there different pulleys or do I need a spacer?
Thanks.
s page

18V engines originally had a short nose pump with a spacer between that and the fan, before that it was a long-nose with no spacer. The pulley is different for each but that is only to align the belt with the crank and alt pulleys, it has no effect on the fan.

Long nose pumps can seemingly be fitted to later engines, so it depends exactly what you have.

There also seems to be a wide variation in metal fans in that some are much closer to the radiator than others even with the correct combination of pump and spacer/no spacer.





paulh4

The 18v fan pulley has a larger diameter hub and will need the spacer--early pulleys were smaller dia. and the fan fits over them ok ---The pic you put up earlier looks as though you have the spacer already---
William Revit

HI all, I made a spacer to fit the new plastic fan. On a hilly run in the Peak District this week the car did seem to run a little cooler with no problems. Whether temp difference was due to the new fan or the new spacer which puts the fan nearer to the radiator. Thanks for everybody's help.
s page

Simon,
did you note what Paul Hunt put on his website (from the link I previously gave) about the standard seven-bladed plastic fan being handed and the deeply sided side of it facing opposite way to what is expected. - (more direct link to this) - http://www.mgb-stuff.org.uk/coolingtext.htm#2010jan
Nigel Atkins

Hi all.
This how I've fitted the fan. Is this right? You can't see the spacer between the pully and the fan.
Thanks.




s page

looks good to me--should do the job very nicely
William Revit

The odd thing is that there was a factory bulletin in 1973 that states the spacer was needed for the metal fan but not for the plastic https://www.chicagolandmgclub.com/techtips/tsb/TSB_no73a01a.pdf

The attached shows an original 7-blade plastic orientated so the curved edge is leading, with the deep dish facing away from the engine. Yours has the same blade orientation but if the spacer is effectively inside the fan boss then the deep dish is facing the engine. The Moss fan is clearly different to the original, so either it's intended for multiple applications, or Moss got it wrong. The adapter Moss show is basically a flat plate with a boss for fan centralisation, and I suspect that goes on the radiator side of the fan and also stops the screw heads pulling through.

Out of interest what is the distance between the leading tips of the blades and the rad core? Tucked under the flange at the back of the diaphragm as you show it does seem to be in about the right position.


paulh4

Paul- I 'think' the fan sp has is the one Moss sells to directly replace the steel fans on MGA-MGB---It's offset rearwards compared to the std MGB plastic fan--

https://mossmotors.com/fan-7-blade-plastic-replacement-for-metal-fan

But needs the spacer for 72-76 models to get clearance on the larger diameter water pump pulley on the 18v engine----With the earlier smaller dia. pulley the fan will sit back over the hub part of the pulley ok and be a direct replacement for the steel fan-as advertised

Having an 18V in an MGA was always going to need a custom fit and sp looks to have come up with an ideal combination
Maybe the fan in your pic. might have been a bolt up job , -don't know, there's 2 different bolt patterns as well, but he's got it sorted now and it should be quite an improvement in an A I'd think-
Cheers
willy
William Revit

Makes me wonder how using the original metal-fan spacer with this plastic fan instead of the Moss adapter affects position wrt radiator. The adapter does seem to have some thickness, but not as much as the original spacer, although the angle isn't ideal.
paulh4

Hi William.
Thanks for all your imput.
There is 20mm between the rad core and the leading edge of the fan blade.
s page

Perfect--

With your 1800 engine, which gearbox are you using-
Why I ask is--The original MGA gearbox mounting is a round metal/rubber enclosed setup which controls any rearward/forward movement of the eng/gbox assembly-
If it has an MGB box or other and the g/box mountings are MGB or other, there's the chance that there's no real control over f/r movement --MGB's have a control rod from the gearbox back to the crossmember-
If you're not running the std MGA box it might pay to have a check underneath to see if there's anything there to stop forward movement, just as a precaution to protect the fan/radiator from damaging themselves under heavy braking etc

willy
William Revit

Not surprised given the apparent dimensions of the adapter to the spacer. 20mm is very little in comparison to several MGBs measured here at more than 1" and fans have been known to chew the rad under heavy braking or frontal impact as said. They have engine restraint brackets round the engine mounts (the clean bit in the attached carrying the carb overflow pipes) and/or a restraint rod between the gearbox and its crossmember, does the MGA have either of those?

paulh4

Hi.
I have a Hi gear 5 Speed type 9 gearbox fitted.
s page

Should be fine Simon-
The Escort/Siera mounting Higear use has fairly restricted front-rear movement.
There are plenty of Escorts running around with std. bobbin style front engine mountings and rely completely on the gearbox mounting to limit F-R movement
Actually, my elan would have a similar mounting and from years of trying I've never had an engine movement issue with it
forget about it and drive on--------sorry if I put the frighteners into you, I just thought you might've been on MGB mountings without any restraint system
Cheers
willy
William Revit

This thread was discussed between 12/06/2022 and 03/07/2022

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