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MG MGB GT V8 Factory Originals Technical - Radiator Questions

Hey Guys,
I'm just about to buy my radiator for my MGB V8 and am concerened with how to go about this, I have three questions any help with these would be appreiated.

1) Horizontal or Vertical flow radiators is there any difference between the two when used in a MGB V8 application?

2) Tripple bypass radiators are they more effective. They have the same cooling surface area area and the engine requirements for water remain the same therefore the water must travel 3 times as fast through the radiator to make three passes through the core. Does this increase the efficency of the radiator?

3) Seperate expansion tanks how do they work? why are they used? and do they have to be mounted approx same height as top radiator tank?

Clem Spriggs
Clem Spriggs

1) The width between the frame rails on an MGB is 18 inches. The height in this forward position is also about 18 inches. The factory used two fans side by side that extended past the sides of the radiator. The two tanks on the sides of a cross flow radiator would narrow the opening to 15 inches or less, wasting even more of the airflow from adjacently mounted fans. A single large fan would be about the same either way. Although you would have the same area for air to pass through, very little air would go through the top two inches up so high above the grill opening.
2) I’m unaware of any triple bypass radiators. Radiators that have three core tubes in depth from front to back, flow all three in the same direction at the same time. Because of the gaps, three tubes don’t cool as well as a single deep tube could. Brass tubes can only be made about a half-inch deep without increasing the thickness and thus the weight. Aluminum doesn’t release its heat as well as brass, but allows deeper core tubes so aluminum radiators cool better overall. At least that’s what it says on the web sites where they sell aluminum radiators.
3) The top tank of early MGBs have the radiator cap built in and are about three inches tall. The later tanks and those on the factory V8s have the cap relocated to a separate expansion tank are only about one and a half inches tall allowing more height for the radiator core. All the air in the radiator will be at the top and will be expelled before the coolant as it heats through the hose in the top tank to the bottom of the expansion tank no matter where the expansion tank is mounted. Again, no matter where the expansion tank is mounted, coolant will be drawn from the bottom back to the radiator as it cools. Repeating this cycle purges air from the radiator, but any coolant that escapes the expansion tank will be replaced by air unless a coolant saver is used. So, an expansion tank is to relocate the radiator cap and the only advantage to mounting it higher than the radiator is which way the bubbles will flow when the temperature stabilizes. It would probably be better to tap the expansion tank off the heater to purge the air from the highest point in the system rather than the highest point in the radiator.
George Champion

Thanks George, that answered two of my questions.

The deal with the tripple pass radiator is not 3 cores but the water flows in the top tank on the left side and then down thought the left most cores of the radiator and then up the middle cores of the radiator and then down the right most cores of the radiator. It does this by baffles in the radiator tanks and is done so the water makes three passes through the radiator. I will scan the advert I saw and post it on a web page it will explain it a little better than my poor words. An advert that I saw claimed it was more efficent, however I figure that the water would have to go through the radiator three times as fast and therefore not spend any more time in the radiator than a conventional type radiator and hence recieve no more cooling, does anyone else have an opinon on that???

Spriggsie
Clem Spriggs

Hmmm. If everything else remains the same, doesn't the fact that the water passes through the rad three times mean the rad effectively has a passage way 1/3rd the diameter but three times as long? Wouldn't this mean that the flow through the rad would be slower not faster? But then again, wouldn't the fact that any one 'lump' of coolant stays in the rad longer (more than 3 times longer?) mean that it would give up more heat? Maybe the end result is very much the same.

PaulH.
Paul Hunt

There is resistance to the flow of the coolant through the radiator and perhaps more with one design over the other but will that make much difference in flow rate? There is a possible advantage to the triple pass design due to resistance in a radiator. If it’s easier for coolant pulled by the water pump to be drawn across the bottom tank than through the core tubes, yet no easier to pull the coolant through the inlet side than the outlet side, then perhaps a standard radiator moves more of the coolant through the inlet side whereas the triple pass would have equal flow through each third.

The answer can only come from measuring the water temperature at the inlet and outlet for two radiators with same area. Did the article show the results of such a test?

George
George Champion

An often overlooked reason for poor cooling is that the coolant passes through the radiator too quickly & so doesn't have time to get cooled. There might be some merit in Spriggies' triple whammy radiator.
Barrie E
begerton@froggy.com.au

The actual water volume in and out would be the same (defined by your pump/termostat) but the flow rate would increase when restricted to a single narrower channel (as in a river does when the banks narrow)
I had a conversation with one of the techies down at Kenlowe when I bought my fan and he happened to be an ex-MG owner. The stock replacement rad does not have a baffle along the top (well mine doesn't)to force the hot water across the veins which gives your key hot spot where the water comes in the top hose to be cooled. This is the point where the single big fan that I bought must be placed. The water will then randomly find the path of least resistance to the exit point which does mean that theoretically it could flow straight down a couple of tubes and along the bottom and out giving you a single hot path (the rest to continue with the river analogy, is a backwater)but as the rad is all open you cant tell where the backwater is. If the path was defined round a single route which forced the water infront of given fan positioning points then two fans would give max benefit rather than just the one covering the hot spot.

Another point is that I think might be right is that the original fans were open blades where as new designs have a outer ring joining the blades which ensures that maximum air is transmitted forward/back rather than the high percentage that would otherwise be thrown centifugally out. This should give more puff per spin.
frank swinton

Hey Guys,
I talked to a Radiator Guy on the weekend and he said the efficiency comes from the pattern of the water flow described by Frank above. He also said a big disadvantage of that style of radiator is that blockages of one core can have a much larger effect on the flow and hence cooling power of the radiator, I'll probably go with the standard setup. Thanks for the help on this one guys.

Spriggsie
Clem Spriggs

Restricting the channel size may well increase the speed of flow through the channel but it reduces the volume - witness what happens as you gradually close off a hosepipe with your thumb. It also increases the back-pressure, which is why partially blocked drains/steams back-up and overflow.
Paul Hunt

This thread was discussed between 30/01/2001 and 11/02/2001

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