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MG MGA - Any new info on fan shrouds
|I'm interested to see if any of you have recently purchased and installed a fan shroud. |
There's lots of info in the archives, but much of it is out of date. Seems there used to be a two-piece metal version as an alternative to the Moss solid plastic. I called the company (Medina Specialty Parts) that sold them and they no longer carry it. Has anyone found an alternative source?
As for the Moss unit, many people complained about it being difficult to install. Is that still the case?
|Ken, I installed the Moss shroud about 10 years ago in an attempt to keep the engine temp from getting too high when driving down here in the summer. I also rerouted my oil cooler lines and added the ducting to the heater. It seemed to help some with the cooling. I don't recall that the shroud installation was all that diffcult. The engine temp runs in the 180s to 190s now when driving around town. This is after getting the head reworked. I still need to get the car out for some extended driving (at least 100 miles) to make sure that everything is working correctly. I wish we would have had more time to drive our cars when you and Melon were here a few weeks ago. Although the wine sure went down good!|
|The Moss fan shroud is easy to install by loosening / removing radiator bolts. I have the Moss supercharger so precious little room on that side and cheat by omitting the bottom radiator bolt. No problems and no overheating.|
|Forgot to mention, I'm sure I emptied coolant, removed the top rad hose, lossened the front air ducts, removed rad bolts, shifted rad forward, jimmied the shroud in place, reinstalled bolts, rad hose and air ducts.|
Tested fan rotation, tightened it all up, refilled coolant.
Cheated by omitting the bottom bolt that is impossible due to supercharger (and the damaged mounting frame from whatever might have happened 35+years ago)
|Ken, I have a plastic fan shroud installed and have had it in for the last four years. It was not difficult at all to install and I found it very effective in keeping the engine reasonably cool. It is not noisy as has been implied in the past, and if installed properly does not vibrate.|
|The Moss description of the fan shroud says that it forces the air through the radiator instead of around it.|
How can the air pass around the radiator?
The body in front of the radiator is itself a shroud if all parts are fitted correctly.
This includes the sealing strip on the top of the radiator and the blanking plate if there is no heater fitted.
The only air not going through the radiator is that required for the SU's.
|M F Anderson|
They work by ducting all the air that does come through the rectangular surface area of the rad to the centre of the rear of the rad. The engine 'pull' fan is almost the same size as the hole in the shroud, hence the greater airflow. Even with all other bits correctly in place, the shroud will make a better airflow. Many people don't have the duct hoses fitted forward of the rad panel so air takes the line of least resistance and goes through those holes also. As well as the Rad sealing strip, i have also blanked of either side of the top of the radiator to close of what are two other air escape routes.
|The original configuration on the air ducts without heater was to have a blanking piece, so there was no air 'leak' past the radiator. |
Is the shroud really trying to compensate for less than optimal replacement radiators?
|The shroud's main purpose is to create greater suction power for the mechanical fan, directing the incoming air through the radiator. Properly designed it decreases the air pressure on the inside of the radiator (HVAC call this the "plenum" effect). At speed this isn't necessary due to the pressure of the incoming, high-speed air. At idle or low speeds is where it really helps.|
Hey Don - When I saw your car during our visit in April, I didn't notice the shroud or I would have asked you about it. Then again the wine may have clouded my vision. Thanks again!
|Can someone post the Moss part# ? I looked in the catalogue , but can't seem to locate the shroud.|
|Edward Wesson 52TD|
The Moss part# is shown on the attached image.
I still do not believe in using them in spite of living in one of the hottest areas there is.
|M F Anderson|
Thanks for the info....I haven't determined if I'm going to use one, but it's good to keep for future reference.
|Edward Wesson 52TD|
|Got one. Love the increased air flow.|
Copy this link and do the same test on your grill.
What we did was see if a handkerchief would be sucked onto the grill before and after the installation. Before it just slid off when the engine was running. After the shroud was installed the air flow held the handkerchief tight to both the grill and the radiator face.
Try it to see
|David - wow! That is an eye-opening demonstration of the effectiveness of the shroud. Is it a Moss unit?|
|While the shroud will limit flow, it should also increase fan effectiveness at low speeds as opposed to the fan basically just spinning in the air without much suction effect through the radiator core.|
I would expect that the shroud would have significant positive effect when idling and at low speeds but might just get in the way of the flow at higher road speeds.
On the race cars I only use the electric fan while waiting to get on the track and once at speed there is no cooling issue at all with a decent radiator core.
|I recently had an overheating problem, due to using block sealer to stop an internal water leak. It worked. But it also gummed up my stock '59 radiator. The car had been overheating even in cold/cool weather.|
After removing the radiator and having it rodded out, I reinstalled it along with the Moss plastic shroud. Wow! What a difference. The temp gauge now stays pegged right at the thermostat opening temp even in hot weather. (It will move up a little in stop and go traffic.)
This all with an 1800 engine.
I actually don't care much for the plastic shroud. I could not get mine to fit flat against the radiator at the top, regardless of how much I tried to pull it tight, which means some air is pulled through that gap instead of through the core. Even with that, it seems to make a huge difference.
I think Barney had located a manufacturer of a metal shroud, and he is able to install his in two pieces which makes installation/removal easier. If I recall correctly, his only complaint was that the metal shroud "sings" or vibrates at certain engine speeds, but best to see his website for details.
I read this thread with great interest. My MGA is still in boxes but one day will have to run cool.
I wrote and article a number of years back on cooling my Sunbeam TIGER - one of the hottest running sports cars to ever come down the line. I intend to use the same principles to cool my MGA as I used on my TIGER. If you want to read it go to:
Under cooling click on Questions and Answers and read to the end of applying results.
I have towed a tent trailer at a crawl, eight miles, up hill, through a constructions site with the temperature in the +118 range and the TIGER never boiled. I kept my right shoe as a souvenir - the side of it got so hot the leather turned brown and crisp.
Godspeed in Safety Fast
|JM - the two-piece metal shroud from Barney's website is from the Medina company I mentioned in my first post in this thread. Unfortunately their supplier passed away and they no longer carry it. They would produce it themselves but didn't save one for a template.|
If anyone has one and is willing to loan it to them they said they would produce them again for sale.
Super info!....So it would appear from that article, that having a shroud is better than not, but it is important that 1/3 of the fan , be exposed, outside the shroud....
This would be impractical in the space on an "A", so my feeling is that the Moss shroud is the way to go....
I'm also going to consider using a rubber seal, under the flange of the shroud, to make sure most of the air goes through it.
|Edward Wesson 52TD|
|JC and Ed: Years ago I had read somewhere about shroud tech (maybe it was your article JC?). I was aware that 1/3 of the fan should be external to the shroud. Note that that is NOT the case with the Moss shroud (at least in my installation). In fact, I was concerned with it because of that. Just eyeballing it, the rear tips of the fan blades are at least 1/2 to 1 inch recessed into the shroud. I even considered cutting off the lip that surrounds the opening (approx. 1/2 inch) to at least get the opening somewhat closer to the tips of the blades but was fearful that it would lose rigidity in that area. I recall wondering if all the fan was doing was roiling air around inside the housing.|
Ed--a rubber seal wouldn't have worked in my case unless it were a bowed rubber seal (never seen one). The shroud is up tight to the radiator at the bolt connections but gradually bows away from the radiator to about 3/4 inch gap in the middle. This all at the top. I haven't eyeballed the bottom. I've considered drilling a bolt hole in the top metal cross piece attached to the radiator (the same piece that the hood prop hooks into), and place a sliding metal finger underneath that is slotted so as to be adjustable that can be used to press against the shroud holding it tight to the radiator at the midpoint.
Further, the fan is not exactly centered in the opening (it's offset to one side) but that's my fault because of having an 1800 in the car with a water pump offset that differs from an A engine.
Even with all of the problems my cooling has greatly improved with it.
JC--can you tell me what the clearance should be between the blade edges and the shroud? I'm considering building my own metal shroud to fit my circumstances.
|Edit to prior post: I would assume clearance between the blade edges and the shroud would have to be at least 1/2 of the distance the engine deflects on the motor mounts (plus about 1/8" safety factor). Anybody have a feel for that figure?|
Close tolerances are not required between the ends of the blade and the shroud. At that point the fan action has turned from sucking to pushing air. Remember the part of my article about blowing through you fist being much easier that sucking through it. This change occurs at the foremost tip of the fan blade. Think of a boat prop. The tip of the prop cuts the water and pushes it back. As the water progresses along the prop it flies sideways off the blade . . . this occurs at about 2/3 of the way back. Air acts in a similar way.
The key is to have the front of the shroud sealed around the outside edges of the rad so that the maximum air is pulled (sucked) through the core. Again remember how hard it is to suck through your fist if there is even a small distance between your lips and your hand.
Shrouds that have open bottoms, rather than ones that completely surround the blades, are not as efficient but tend to force more of the air down and out of the engine compartment. The problem with this is that at idle the air hits the pavement and then circulates forward, through the grill and back through the rad gaining heat. This should not be as much of a problem with an A as it is with a TIGER because the A has a better designed bottom pan in front of the rad.
A wind tunnel and smoke test would be the way to really design efficient cooling system for the A.
This of course is only my my own interpretation and experience of how it all works and I would welcome anyone with real knowledge correcting any misconceptions that I have.
Pix 1 of my TIGER's shroud
Godspeed in Safety Fast
|Pix 2 of my TIGER's shroud. You can just see the fan with 1/3 of the tips of the asymmetrical 5-bladed fan exposed. As a point of interest this fan bolts up to an MG water pump. Hard to imagine that the A would be a tighter installation.|
This thread was discussed between 03/05/2013 and 13/05/2013
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