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MG MGB Technical - Seven blade fan

Hi guys, I have a 1967 BGT can I replace the three blade metal fan with a seven blade plastic one, is it a straight swap, and where can I get one?
I'm assuming this will help with cooling and reduce the drag on the engine being plastic.

Cheers
Jack New Forest

I think you'd need to change perhaps the spacer/clamp too but first check for wear on the rubber grommets and try replacing those before changing fans

also of course check the fan belt is not loose and water pump is fully functioning

you shouldn't need to change your cooling system on an engine set that's pretty standard provided your whole cooling/heater system is thoroughly clean and all components and parts fully functioning and with the coolant itself in good condition (the coolant element wears quicker than the anti-freeze part so regular changes are required) and topped up

something as simple as having the correct rated pressure cap and it being in good condition can make a difference

my mate moved his front number plate a bit on his TVR and the temperature gauge readings dropped, a no-cost improvement instantly

same for secondary cooling system, the oil, regular oil and filter changes and kept fairly topped up - if you have an oil cooler fitted an oil thermostat will help to prevent over-cooling the oil on many occasions
Nigel Atkins

I believe that Moss Motors carries them. The mounting holes are the same as the original fan. I made the change on our 66 MGB, more that I was concerned about a heavy steel fan blade coming the bonnet than for cooling. I can't say if the cooling is better with the 7 blade fan than with the original. As for belt tightness, if you car still has a dynamo rather than an alternator, keep the fan belt quite loose to avoid premature on the rear bushing in the dynamo - see the article, Keep Your Belts Loose in the Other Tech Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
D W DuBois

Jack,
I fitted a 6 blade injection moulded fan from NTG to my 3 bearing mgb engine and it brought the normal running temperature down from 185 degrees F to 175. it certainly moves much more air than the standard fan but at the expense of being very much noisier, you can really hear the above the engine noise especially when the engine is revving hard.
I have heard that the 7 blade fan from Moss is much quieter because of its clever asymmetric design.

As for being easier on your engine, it depends on your point of view.

These fans will definitely cool your engine better, but because they are shifting more air, they wil probably take up to 1 or 2 more bhp to run than the standard fan.

In other words, Reduced coolant temperature VS Slightly increased fuel consumption and slight bhp reduction.
c firth

Are you having cooling problems? If not don't bother, if you are look at why! The fan is only serving a useful function up to about 6mph. As said above the multi-bladed plastic fans are noisy. I have one, you can have it, it sounded like I was driving a hovercraft. I put an electric fan on, which hardly ever came on anyway.
Allan Reeling

Thanks for all the info guys, as per usual you have been a great help, I don't know what I would do without the forum it's great.
The problem I have, last weekend I was at Le Mans Classic, the drive down was fine, when I'm driving normal speeds temp is fine just below halve way,
The problem is when I get stuck in traffic, the temp start to climb to hot, then with engine bay really hot and not going anywhere, I get the engine starting to misfire and like vapour lock or something I'm worried I'm going to blow a water hose or worse.
I have fitted a new thermostat, new radiator cap 10psi hose and coolant in good order.
My next step is to fit a kenlow which a friend gave me, I think that might be the answer, my BGT just does not like sitting in traffic.

Cheers
Jack New Forest

"I get the engine starting to misfire and like vapour lock or something I'm worried I'm going to blow a water hose or worse."

This has nothing to do with the cooling system. If it's not losing coolant-it's isn't overheating. You have a different heat dependent fault. These cars run in Hot US states, and vapour lock is pretty near a myth under normal driving (queuing) conditions. Tho the heatshield under the carbs needs to be in reasonable nick.

HS4 carbs don't like idling for too long-you need to blip the throttle to clear them (and this will shift a bit more air thru the rad)
Michael Beswick

the engine driven fan whilst it does the job isn't best for use on a cold engine as it still tries to cool and when you need it most when stationary queuing it going at it's slowest (and conversely going quickly when you don't need it travelling above about 40-50+ mph)

I'm with Mick blip the accelerator every now and then, it'll also spin the water pump more - check that your idle speed isn't too slow too

whilst your car is not overheating it may be like many classics and carrying a lot of muck ad crud in the cooling/heating system

rather than go into my very easy but thorough coolant/heating cleaning system here I'll send it to you if you want it, just email me


apologies in earlier post I meant check the fan belt isn't (too) loose
Nigel Atkins

Ok Michael and Nigel, I'm going to stop worrying, that is what I was doing in heavy traffic, I just blipped the throttle to keep it going,
I just thought I shouldn't need to do that. I'm going to fit the kenlow and check my coolant perhaps clean out the old stuff, yes Nigel if you can send me you step by step guide I'd appreciate it.
Email is:

jacktorrance@hotmail.co.uk

Thanks to both of you and all the other comments.

Cheers
Jack New Forest

This thread was discussed between 13/07/2014 and 14/07/2014

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