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I am interested in removing the metal fan unit and put on a MGB plastic fan unit with more blades for better cooling. Does anyone know if this will work and what might be the problems with this set up. I am running a 18v engine 5 main. I also have a Judson supercharger on the car.

Jeff, Colyn Firth (no, not Colin Firth!) has one of these fitted. He will probably give you a reply, but he says although it is rather noisy it cools well. I believe you have to move the rad forward a bit so that the blades don't hit it, as they flex a bit at the tips. I reckon that if you over-rev the engine with one of these fitted you might just take-off!
I took my metal fan off and fitted an electric fan. It works well here, but I think it may be a little warmer where you are!
Lindsay Sampford

Lindsay is correct Jeff, I have fitted a 6 blade injection moulded fan from MG Bits4U (NTG Services) and it really works well.
It has a much more efficient blade design, is a little larger in diameter than the standard MGA metal fan and moves a lot more air too. (enough to blow my baseball cap off when I first revved it up)

The MGB water pump is apparently a little longer than the MGA pump and you may have to space the rad forward a little.

On other cars I have seen evidence of the fan blade tips touching the rad in really hot conditions when the blades may flex a little more, but it has not happened on my car.

If the blades on your MGB fan are very bendy you may have to allow extra space between them and the rad to make sure there is no contact.

My new fan has dropped the usual running temperature from 175 degrees F to 165 degrees but at the expense of making it howl like a double-decker bus engine!

I am going to fit an electric fan over the winter to see if this works well enough.
It will be good to hear the tappets again!

Colyn Firth

Jeff, if you look at Colyn's picture you will notice that this new fan works so well that he doesn't need a radiator!
Lindsay Sampford

Jeff, I fitted a plastic fan of similar style to mgb and found much improved cooling when in a queue or going slowly in traffic even on days when the temp never gets past 200 degrees C. However it does not alter the marginal performance of my engine when on a motorway at 70mph + on a hot day especially on an incline when it reaches 212+. You may need a double layer of felt packing to move the radiator forward as CF says.
J H Cole

JH, have you tried opening the grille slats a little? I had the same problem until I opened mine. If the engine runs hotter at high road speed than it does at 30MPH, it is usually caused by lack of airflow through the grille.
Lindsay Sampford

LS I have tried opening up the slats to the stage the're now at but I wonder when to stop? My feeling is that the problem lies with the sheer amount of heat energy that has to be dissipated when at speed and that's when the radiator is marginal. My radiator has been recored and the rad man convinced me some 8 years ago of the merits of the replacement that has more fins but less free airway. At the time I didn't know what I now know on this whole subject. Its not too much of a problem now since the UK seems to no longer have any hot weather.

J H Cole

JH, they look quite open, and you have the MKII 'air-scoop' type grille. I wonder if something else is causing you to run hot. Apart from a faulty thermostat, retarded ignition is probably the biggest contributor to hot running. Weak mixture is another possibility. My car will run all day at motorway speed with no fan and sits at around 190F, so a big plastic fan is not likely to help you there.
Lindsay Sampford

I might be lucky, but I have a bone-stock '57 1500 with original grill slats (not turned), and an original radiator, and I run at 190* in the summer with no issues. T-stat is a 189* unit, AFAIK. Always gets to 190* and then stays there. (Gets to 210* after shutting the engine off if the engine has been pushed hard, but then comes down again soon enough.) Timing set to about 10*BTDC static, using original points ignition.

This spring/summer was it's first return to road-worthiness since 1978.

I am not sure why others seem to have so much trouble with this. There has to be a root cause, so that electric fans and the like are just a fix for the symptom.

Are there many sub-standard replacement radiators out there? I would think that the relatively odd/rare radiator cap style would be a big culprit - you do need a 7 lb. long-neck style cap or you will not get the pressure build up in the radiator, and temps will rise.

Another thought - do many higher mileage cars suffer from fouling of the water channels in the engine blocks?

Someone mentioned that I should put in a 160* T-stat instead - what would that accomplish? What is best in a moderately temperate climate like the northeastern USA or Britain?

AJ Mail

Jim, yours sounds like it is running perfectly so don't let anyone persuade you to change anything! You are right about radiators. Some don't cool very well at all, like the one I fitted to my car before I had the 'original' re-cored.
Lindsay Sampford


I am like you. Everything standard and works fine. I have often said on this forum that the root cause of many problems is a non standard core radiator. For some time I was running at only about 150 degrees until I recalibrated the gauge. I now run at 175 day in day out!

Steve Gyles

Doesn't matter what thermostat I put in my car, it runs at 70C in the summer and at 50C in the winter unless I close the radiator blind or fit the grille muffs, then it goes back to running at 70C again. Without the Judson the temperatures rise by 5-10 degrees. On a hard long climb at speed (Klausen Pass for example,- though speed is only possible if there are no dutch tourists on the road having escaped from the Berner Oberland!) it will get up to 85C. The gauge reads 100C when the bulb is in boiling water, so it is spot on.

I suspect many people have the wrong radiator core (mine is bog standard), timing that is a little too advanced, mixture that is too lean or water passages that are full of crud, or a grille that blocks too much air (or a combination thereof). I wonder how much of a difference the mesh grille makes here.
dominic clancy


Just as a matter of interest how high are you above sea level in your part of switzerland?

Steve Gyles


Just looked it up. Your gauge is 2 degrees out. Water boils at 98 degrees C (209 F) in most parts of Switzerland.

Am I right in thinking that you swapped the engine during last winter and the new one is still reading low?

Steve Gyles

Fan fits with the same year pulley and water pump. Plastic fan is from 1972-76 MGB.
M. H. Dabney


Zürich is only at 500m, so not high at all
dominic clancy

This thread was discussed between 19/09/2011 and 30/09/2011

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