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MG MGB Technical - MGB fan shroud, 77-80 twin fan
|Does anyone know of a fan shroud that will fit the 77-80 MGB with the twin electric fans? We have had a series of days above 95F/35C, and the cooling system has been taxed to the limit in traffic and a couple of trips above 11,000 ft. In looking at the setup as the factory supplied, there is a lot of turbulence at the end of the open fans and air is going around the radiator instead of through. The car does not overheat but the temp gauge is well above the normal zone at these times. Ben|
|I have never seen nor heard of a shroud for the twin fans? I dumped them from my car and fitted a decent modern fan behind the radiator. A puller is better than a pusher fan and also the modern ones have a shroud to avoid flinging all the air around the radiator as you mentioned with the originals.|
|Ben. I do not know of such a shroud, not do I know how one would be possible. With the pusher style fans used on the later model MGBs, a shroud would restrict the airflow to the radiator at road speeds. Exact opposite of the effect when using a puller type fan system. |
As to your exact problem--the gauge reads high when in traffic or at high altitude, may I recommend the purchase of an infa-red thermometer? I had a fellow come over because his gauge was reading above the 3/4 mark and he thought he was "over heating". We checked his actual cylinder head temperature which was an average of 183 deg F when the gauge was reading 3/4 of the way to max. In reality, tests have shown that this is a little cold for maximum engine performance and engine wear characteristics. A hot engine, according to the tests I have read about, wears less than a colder running engine.
Here in Arizona, where the ambient temperatures can run well over 110 deg F, my 68 GT will go to almost max on the dash gauge. Especially so in stop and go driving on the limited access highways. The car still runs well and there have been no problems with head gasket failure or warped cylinder heads over a period of many years. The maximum temperature observed has been about 232 deg F which is not excessive considering the boiling point of pure water (about 210 deg F at our altitude) the 21 deg increase due to the 7 psi radiator cap (raising the boiling point by 21 degrees) and the 25% AF in the cooling system.
In your case, you have a much heavier radiator cap raising the boiling point significantly higher (three deg F per one PSI of pressure) and a better design of radiator. If I were you, I would not worry about it unless I was loosing water from the system. Then, I would replace the radiator cap first.
If you can afford an infa-red thermometer, the less expensive ones read to 500 deg F and are about $70, you can check out the actual running temperature of the cylinder head. It might prove a surprise.
Not all of your heat is just the radiator and the motor. A lot of the heat is from the engine compartment itself. I have a light on the dash that tells me when the fans come on. It lights a lot of times when the motor temp show OK! where is the heat; it is in the engine compartment and is slow to get rid of. I have an 80 and the original fans. I use a adjustable thermostat on the radiator to turn on the fans when the gauge gets to midway or straight up. No problems since I installed it years ago.
|Dale & Barb Mast|
|I think Ben is right in that the original fans are inefficient. If you look at any modern rad fan the blades are joined at the edges by a circular shroud and I believe this prevents lots of air spilling off the tips of the blades. Also, the original fans are not always fitted very close to the radiator core. Ideally they should be as close as possible without actually touching. Any gap will cause lots of air to bounce off the surface of the rad and be lost instead of forcing through. Most efficient is undoubtedly a fan between the engine and the rad. Not much room on my '71 car, though there should be room on the later car.|
With regard to Les' comments, we in Scotland don't get Arizona temps, but when my electric fan failed in heavy traffic in Glasgow I watched the gauge rise to 220 degrees F indicated and it never boiled or even mis-behaved.
The GTV8 runs in similar temperatures with the same fans and pretty much the same rad - as Mike says; you need to get the blades as close as poss. to the core.
Yes a puller fan may be more efficient - if it fails you are up the creek without a paddle !
This thread was discussed on 10/08/2005
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