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MG MGB Technical - New rad required, 2,3 or 4 tube core?

Hi all,
Promise I won't make this a habit. The following relates to my MGB 1800 engine installation in my MGA, but as the standard rads are virtually identical, I am hoping to pull on the experience of MGB owners as well as "A" ones.
As the title suggests I need a new radiator core. I visited the radiator shop this morning and discussed my options, apparently any of the above will fit. It was suggested to me that just installing a 4 tube core would not necessarily improve the cooling situation (1800 MGB engine fitted). I know that others have experience of fitting a 3 or 4 tube core, in place of the original 2 tube one. Would anyone care to share their findings positive or otherwise? Perhaps I should add that I have dispensed with the engine driven fan and added louvres in the bonnet in an effort to help air movement - and that I intend to tow a small caravan, so efficient cooling will be imperative. Thanks in anticipation.
Tony Mitchell

I believe a 3-row core is considered as stock
replacement for MGB (I may be wrong on this).

I have a '71 B/GT with 3-row core, 6-blade large
engine driven fan, OEM-type water pump (not
aftermarket), 180º thermostat.

Here in Southern California, it is just adequate
for the job during pleasant weather, only.

During warm-hot weather (85º +) I have to keep the
car moving forward ...just as most sharks must
keep swimming forwards, or die.

If I get stuck in traffic, or have to wait for more than
2 traffic light cycles then the Temp guage needle
will quickly rise to alarming levels.

The Temp guage will also nag me while driving
long up-sloping stretches of road, or hills, in any
sort of warm weather, at any speed.

My next radiator will have a 4-row core.
Daniel Wong

Going from 3 row to 4 row gives a lot less than 30% better cooling because of the law of diminishing returns, by the time the air gets to the last row it is pretty hot already. I fitted a four row to my V8 as the temp gauge got much higher than I was happy with in hot conditions, but I was disappointed with the results which was only a marginal improvement. I got much better cooling by beefing up the electrics of the cooling fans, the original design of which is pretty poor.
Paul Hunt

The problem is that you can't fit a fat core in an MGA without cutting the front shelf. For this reason I fitted a 2-row MX core, which is a two-pass core (tube inside a tube) in my MGA, which is equipped with a 3-main 1800. You MIGHT fit a 3-row but it's really tight and I wasn't comfortable with how close my fan would be to the fins. A short nose water pump would solve this problem but the block will require machining (if it's a 3-main) and I wasn't willing to do that do a freshly rebuild engine.

In normal weather the running temps are fine, but in 100+ degree temperatures the car does run hot, and sitting in Summer traffic will take it into the danger zone. Next time around I will probably do the water pump mod and go for a 3-row core.
Steve Simmons

Tony-
My engine is heavily modified (1924cc, Derrington head, etc, etc.), and I used a four-row core. No overheating, even on hot days. If you're going to tow a caravan, you'll need all of the cooling capacity that you can get.
Steve S.

Daniel, Do you drive with crossed fingers coming up to the lights?
Paul,
Are you saying that the 4 row IS an improvement,just not the full 30% that you expected? My radiator man suggested that it may be NO better if the airflow away from the radiator is not good, as in MGA. Certainly if cooling is improved even only marginally then I feel that the change would be worthwhile.
Steve,, Virginia, You seem to be delighted with your 4 row.
Steve Cal, Not too sure what you are saying about the 4 row core - so long as it fits the tanks then surely it should fit in its original position. The standard core is much narrower than the tanks (front to back), so there is space. I am with you on the short nose pump - I intend to use that to give me space for a puller electric fan behind the rad.
Thanks all for your input and time it is greatly appreciated. Tony
Tony Mitchell

Tony - the 4-row gave a marginal improvement, certainly not what I was expecting or needed, and certainly not worth the extra money. I got better than I expected from beefing up the electrics, which cost me nothing except a little time and thought. Whilst the MGB even a rubber bumper possibly has better flow through the rad while moving than an MGA it's at idle that problems occur and I doubt the two are much different. Certainly the MGB and I'd imagine the MGA is the same in that the fan(s) have to force heated air downwards i.e. contrary to physics before it can escape around the bottom edges of the engine compartment, little will escape down the tunnel I suggest, and even then it can only escape downwards. At a standstill and in still air about 25% of the hot air comes *forwards* to be recycled through the rad reducing cooling capacity still further. Some years ago I was on a run where we were each interviewed at the finish line. Everyone's temp gauges started spiralling upwards as we had a slight tail breeze which pushed even more hot air forwards to be recycled, and people were getting panicky waiting in line. This is why people cut RV8 holes in inner wings even if they don't use them, and sometimes bonnet louvres, which means hot air can escape from a higher level and less goes forwards to be recycled.
Paul Hunt

Tony, the problem isn't the size of the tanks, but rather the space available between the engine and the front shelf. The radiator hangs below the front shelf, so moving forward is not an option without cutting metal. That leaves only the empty area behind the radiator available for a larger core and there isn't a lot of space to be found.

Paul, the MGA has a narrow grill opening with far less air flow and the engine bay is a lot smaller. I have experienced far more problems cooling my MGA than any of the Bs, as have many acquaintances of mine who own both, especially with 1800cc and a stock fan. I do enjoy originality but I plan to try a flex fan this Summer to provide better cooling! My Bs have no real heating issues with stock fans.
Steve Simmons

Tony-
Be advised that at highway speed it is primarily air pressure in front of the radiator that forces air through the radiator matrix, not the fan. Air pressure tends to take the path of least resistance, moving through any open spaces in and around the radiator-mounting diaphragm rather than through the radiator matrix. Therefore, if you want the coolant system to function to maximum effect, be sure that all of the spaces around it and above it are well sealed. However, do not seal the circular apertures in the radiator diaphragm as they are present in order to allow needed cooling air to vent into the engine compartment.
Steve S.

A good point, even though I have never had cooling problems on my roadster when I added the foam seal between the top of the rad and the its mounting plate after many years I'm sure it runs slightly cooler in warm weather.
Paul Hunt

Tony
You state you "dispensed with the engine driven fan". Does this mean you have installed an electric fan or do you have no fan at all? Even in cool to mild climates the B engine needs help when idling or moving slowly in traffic. As stated by others, changing the core will help but you definitely need to pull or push air through the radiator.
Lee

Tony - IIRC, in Graham Robson's book, he describes the MGA grille as "cleverly designed to block airflow to the radiator".

What's been the experience of A owners, especially regarding the flow through the grille and into the smaller engine compartment?

While a four row would help, based on coolant capacity, the basic physics is more dependent on air flow, as the other posters have mentioned.
John Z

Tony -

No, I do not cross my fingers when rolling up to a stop light.

I survey the cars in front of me, clench my teeth, and pray.
Daniel Wong

Keep in mind that most aftermarket MGA grills have the slats closed too far. It looks nice but blocks more air than it's supposed to.
Steve Simmons

Tony,

Over-heating in not the only problem.

The additional weight of the caravan will be more stress on the braking system and rear suspension. How much will the caravan weigh? Will the caravan have surge brakes? Tongue weight is also critical. Have you modified the rear springs? Just hooking up a trailer requires more than just a hitch and tow bar.

I have towed a sailboat over the mountains to Lake Tahoe with my GT. The mountain pass at Donner Summit is nearly 8,000 feet. The engine and gearbox handled the 1000 pound load but in addition I had heavier rear spings and surge brakes on the trailer.
Lee

I added an electric cooling fan in front of the radiator in my '66B. The engine is lightly modified, and I found that I had the same problems as everyone else--overheating in traffic. The electric fan pretty much cures that. I have it wired to a switch on the dash, so I only turn it on in traffic or at lights. I also have a recored radiator that is heavier than stock (can't remember exactly what.) The electric fan makes a bigger difference.

Oh, and I've towed an MGA with my MGB uphill with an electrical extension cord. The extension cord kept breaking so I couldn't down shift to climb hills. I lugged the engine down below 2000rpm and the B kept pulling. Overheating wasn't an issue, and this is before I rebuilt the engine. You can pull a lot with a B, but I'll second the advice on trailer brakes.

Chris
Chris

A lot of information! All the pointers seem to indicate that the detail is important ie, sealing around the rad to make sure that all of the available air passes through the rad. On that point I intend to manufacture a shroud to enclose the rear of the rad, just leaving an aperture for the fan.
Yes Lee I have installed an electric puller fan with a thermostatic switch and an override switch on the dash. I have also done quite a lot of caravan towing - though not with the "A", the caravan does have surge brakes (overrun brakes in the UK), the caravan is quite lightweight 700kg and probably not seen in the USA it is called an Eriba, Google it they are perfect for our kind of motorcar. A friend of mine tows one very successfully with his MGB engined "A".
Thanks again for the input.
Tony Mitchell

you might consider a scoop underneath the front bumper with some holes in the front valence.
jjralston

jj - just where I have fitted the oil cooler! Thanks
Tony Mitchell

The V8 has the radiator projecting below the apron, and on rubber bumpers the oil cooler is that side as well. There is a fibre-board sheet behind two holes in the valance which is meant to direct air onto the cooler and rad, but on mine instead of being rectangular it was arched, leaving big gaps to the side and the bottom. I used an alloy strip to force it into a rectangular shape which now fits much closer to the outline of the rad, and it did make a difference.
Paul Hunt

This thread was discussed between 19/03/2009 and 25/03/2009

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