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MG Midget and Sprite Technical - Some info wanted on Midget heater cores

I have wandered over here from the MGB forum to see if I can find out any info on the later heater cores used in your midgets. Specifically, I am wanting dimensions of the later cores, and, if possible, an explanation of how the coolant is routed through the core in order to allow both inlet and outlet nipples to be mounted on one end?? I am thinking that the core must be divided in halves one side allowing coolant to come in, go thru one half of the core, pass thru the other tank, and then back to the origin tank and the outlet there. I am assuming a baffle dividing the nippled end tank.

Regardless, I would appreciate some info on just what the realities are. Dimensions (equivalents to those shown in the sample MGB core in the attached photo), and how the later cores actually did their work.

Thanks in advance!! Bob M.


BobMunchausen

thought I'd bump this as I'm sure some of you will have heater matixes stacked in your sheds somewhere

and someone will know about internal construction
Nigel Atkins

Thanks for bumping Nigel. It would just be info that would add not only to my own in pursuing this "project", but could very well be worth something to someone else, another Midget owner perhaps. Thanks!!! (bump!)
BobMunchausen

FYI - you could go here, http://forums.extremeoverclocking.com/showthread.php?t=98905 , locate the zip file in the posts. Some info of some value.
BobMunchausen

Bob,
I have looked at your informative site many times over the years and wish I could help you, but my Midget has the early heater with a pipe on either side, just like the MGB item. Are you planning to alter you MGB unit to take one of these? When I built my V8 GT and after reading your piece on the crummy valve used on the MGB, I altered the heater plumbing to use an in-line ball valve. It works great from the original fascia control and is so much better.

Mike
Mike Howlett

Mike,
In a discussion about MGB heater efficiency, a Midget owner from the Midget forum on another MG site brought up how installing his late model Midget core into his MGB heater gave him more heat. When viewing the core he showed, it looked to me as tho it was set up differently from the MGB core (see photo). Therefore, I was just pursuing why this greater efficiency would be true. It could be that it is the magic bullet to MGB owners long quest for more heat. Or maybe not. But to try to understand what was going on, I thought you folks would have the greatest fund of knowledge about your car's heating system, and maybe some better photos????


BobMunchausen

Bob,
Sorry, you don't seem to be getting much response - which I have got to say is unusual for this BBS! Usually by now the topic would have been covered in depth from all sides and we would by now be debating Prop's proposed use of truck bed liner as a head gasket sealant.

All I can say is that my heater core is of the type with two pipes at one end. But it is installed so I cannot give much more detail. I think it is set up effectively as 2 radiator cores side by side. The water flows in through one connector and through the finned pipes to the tank at the opposite end. This tank spans both rad cores so the water then flows across and back down the other to the outlet pipe. The tank at the connector end would be divided, or made as two tanks. I think that is the arrangement, giving a rad surface area twice that of the apparent size.

If I am right then it would make a slight difference which way the water flowed in relation to the air flow. One would want the cool incoming air to come through the fins of the second stage rad first so as to optimise the air/water temp differential on each.

But this is speculation. As with the Higgs Bosun you now need to find the evidence to prove the theory.
Guy

just proves that Midgets are for men and B's are for softies - heaters? - bah!
David Smith

so that's how the foam supposed to go - my foam was too short to do that

getting all the seals around the matrix and heater box certainly help with getting the heat to the cabin

and on a B reducing the draughts from outside, the hood, door seals and that fresh air flap

surely Dave O'Neill's got a stack of them and can spare one to cut in half :)

my mate's Rover P5B has a second heater matrix for the rear seat passengers to have additional heat if they want, he didn't know it was there until he had to drain the coolant

he managed to refill from an unmarked plastic can to discover it was wheel cleaner - he marks up all his unlabelled cans now :)

he had a spare s/h matrix and you could see the end tanks of it were blown outwards, no matter how much I cleaned, de-scaled and flushed it out you could still hear scale inside it, the perils of using tap water :)
Nigel Atkins

Personally I dont understand the issue with the heater... I certainly don't think its worth the effort of stripping one to put in a larger core.

My heater is fantastic... after 5 mins I have to open the window cos its too hot... even when I shut off the box...

maybe I should turn the temp down!
C L Carter

Christian,
I agree with you about the heaters in the later Spridgets and great you’ve got yours working well but Bob is after getting more heat into a B

you have to open the window because you can’t shut off the box it just diverts to windscreen instead – as Daniel sometimes says ‘ you can get books on this ‘ :)

to turn the temp down in yours . . .








. . . well, er, is obvious :)
Nigel Atkins

I have a Midget core in a box in the garage - unfortunately buried. Hopefully tonight I'll dig down and get it out for measurement.
Dean Smith ('73 RWA)

Ah, mis read the post then. Didn't realise it was for a B. Too much air to heat.

Nigel, in the 1500... you shut off the box entirely. There is a big butterfly valve operated by pulling the heater knob out of the dash.

If you close the flaps by the footwell then thats when it diverts to the windscreen.
C L Carter

>>There is a big butterfly valve operated by pulling the heater knob out of the dash<<

yeah and that stops the ram effect of the air entering the box from the trunking, the air is still heated and gets in the cabin

the valve is before the heater not after

I don't think you've got the hang of the heater yet :)
Nigel Atkins

Nigel,
On mine, very little hot air gets in the cabin if I close the big butterfly. It seals pretty well and with no incoming air to the heater box, although the heater matrix is still heated not much movement of air takes place from there into the cabin. Only in hot summer weather do I find it necessary to open the bonnet and close the tap on the head. If I had to more often then I would probably rig up a remote system like Lawrence's but for 2 or 3 occasions a year it doesn't seem worth it.
Guy

Guy,
my valve closes fully and the seal is in good condition, in fact only the other week I had to remove the trunk/heaterbox adapter/joint (what is it called?) that has the valve so I lubed the mech and checked the seal

with the heat I get from the matrix even with the valve closed if I have the roof up I couldn't have the heater (tap turned) on in autumn let alone summer without having a window open, differece between here and Cumbria :)

my point has always been that to someone not used to these types of cars the heating arrangements are not logical and as they would expect from the cars they've grown up with and are used to

there is a clear and open box and ducting that can take heat from the heater box to the cabin unless you stop the car, lift the bonnet and turn a tap or lever, this was antiquated in the 60's let alone 35 years later
Nigel Atkins

Don't fret Nigel. I am not arguing with you.
It never occurred to me that you meant with the roof up! I rarely have the roof up on my car - except in a particularly wet December!
Guy

I'm a soft southener :)
Nigel Atkins

So mine is from a '73 MK3 Midget (1275 RWA)...other heater core's may be available. Its identical to the picture from Bob above.

The inlet/outlet are on the short side (depth in your diagram) rather than the long side (width).

Measurements below are in the same orientation etc as in your pic.

Overall Length 253mm (10")
Tank Width 103mm (4")
Tank Depth 57mm (2 1/4")

Core Length 208mm (8 1/8")
Core Width 102mm (4")
Core Depth 50mm (2")

(sorry - the only tape I had to hand was metric, conversions are my approximations)

As you can see the tank on the end with the inlet/outlet is split into 2 - the far end isn't. So flow would be along on side and back the other.


Dean Smith ('73 RWA)

Thanks for the help. Didn't realize it would start such a conversation! BTW, remember, an MGB heater doesn't have a means to damper down the influx of air into the heater like your Midgets apparently do. Whatever gets rammed into the cowl vent goes directly into the fan intake and on to the core.

I am posting a photo for you of the later Midget core's coolant path that another enthusiast passed on to me the other day.


BobMunchausen

just a note

when fitted in a Spridget that matrix would be the other way round with the inlet and outlet pipes placed at the opposite end - putting the inlet at the bottom
Nigel Atkins

This thread was discussed between 07/01/2012 and 18/01/2012

MG Midget and Sprite Technical index

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