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MG Midget and Sprite Technical - Alloy Radiator Upgrade

Hey everyone,

Im back for more! Never get my head around how much knowledge is on this place.

I've been looking into getting a fancy cross flow aluminium radiator for my '67 MK3 midget - it currently runs a standard vertical flow job.

Is it a big job to swap these over? Is it even possible? I mean I don't even know if it'd fit...

I'd normally run out side and measure up, but I'm at uni right now and 200 miles away from her! I've got big plans for a summer-long rebuild including a new 1340 engine, 5-speed and loads of tinkering...!

Thanks in advance,

Josh Spooner

By the way, I've seen this which looks like a steal:

(Hope I'm allowed to post this here!)

What do you think?


Josh Spooner

Hi Josh,
I've got a standard downflow rad on my 1330 which seems to work fine even while sitting in heavy London traffic. at motorway speeds+ is also stays cool. What is the reason for cross flow aluminium radiator?
Is it the bling factor or for weight saving or thermal efficiency?
G Lazarus

I had an aluminum made several years back, I absolutly love it, only down side in fall and spring its hard to bring the temp up to normal

Look on ebay, lots of aluminum china made rads there .... the ones by champion have a good following ... I only seen one break so far, and it was re tig welded easily

There not a hayens manual fit per say ...they do require some fiddling to install but well with in reason of the avgerage man with a pocket knief and a baseball sized rock as a tool collection

Here is an ebay link for one of theres

ebay # 251142855297

Prop and the Blackhole Midget

Like-for-like, ally is less efficient at cooling than brass AIUI. Modern construction techniques allow greater tube density which is how the extra efficiency is gained in specialist ally race rads. The weight saving is 0.9 kg, hardly significant in a road car. So it comes down to bling I guess. BTW the above tech bits are from Daniel's book.
David Smith

I'm glad the others have put as they have about the merits or otherwise of ally rads and Gary confirming the downflow rad working in his car as I'm sure you wouldn't having accepted the info from me

it is important to have the whole of the cooling (and heating) system clean, including from the engine drain, and all the components of cooling system clean and in good working condition including the coolant

many owners seem to get improvement by 'upgrading' components simply because they change the coolant and are replacing a crudded up component with a clean (new) one
Nigel Atkins

Hi everyone,

Thanks for replying so quickly!
The reason's two-fold really. Firstly, my radiator's knackered and needs replacing - to get it recored I've been quoted 168 inc VAT. The whole engine and gearbox are coming out and being reconditioned/replaced and I just want to give it the best chance of staying in good nick for as long as possible. I'd heard alloy rads were better but as you rightly say, there are obvious downsides.

The reason I even started looking at alloy ones at all is that I can get one for just over half the price of a standard unit.

So I guess really it's a cost issue for me, rather than necessarily wanting to upgrade it particularly.

Hmm...I guess I'll have to see. Thanks for the info on swapping one in anyway, if it comes to it I'll make up some brackets etc. Just wanted to know if it'd be possible!

Thanks very much as always guys.

Josh Spooner

Like for like metals the downflow radiator weighs more than the crossflow and more still when full of coolant. However, the crossflow rad needs the crossover pipe (I had one made in aluminium to save weight)and an expansion tank. I that that also answers your questions about converting from one type of cooling system from the other except you either need a shroud or to make brackets.

The aluminium alloy rads save weight and improve effiency for the very reasons that David states. However, it's possible that in service the aluminium unit lasts longer than copper brass (goes longer between re-cores).

My 69 Sprite is 2kg lighter than it was last year and I hope to drop the weight a bit more again this year. Another 900 grammes would be a welcome find (at the right price)!
Daniel Stapleton

if you shop around you'd get a new vertical radiator for less than 168 and possibly a lot less - I've no idea of the quality but then I remember threads on poor quality ally rads too
Nigel Atkins

I forgot you also need to swap the thermostat housing and hoses!
Daniel Stapleton

And, the crossflow rads can operate at a higher pressure than the downflow rads so with the higher poundage cap, the engine can get hotter before venting steam!
Daniel Stapleton

My 1380 stays nice and cool with a normal vertical flow rad.
So for cooling capacity it is not needed.

Just keep it clean block the bypass hose and always have your heater tap open.

And ask Arie how long it can take to get a good alloy radiator.....
Onno K

the crossflow rad in my K series conversion cools it beautifully, no need for anything extra in my case.
Rob Armstrong

I had an expensive ally rad on my MGB V8, thinking it would be the bees knees. It wasn't and it leaked. The supplier was ever so good and tried to get it fixed, and when that failed gave me a second one as a last ditch gesture - it was then three years since I'd bought the thing. The second one also leaked.

I took it to a radiator shop in Glasgow where they were making all sorts of marvellous radiators for some very old cars, as well as sorting out modern stuff. The guy there hated ally radiators because (a) like for like they are less efficient than copper/brass and (b) if they leak they are almost impossible to repair, unlike a copper/brass one.

In the end I ditched the ally rads and bought a copper/brass one. It works perfectly with no sign of the car overheating even in warm weather and heavy traffic (and an MGB V8 makes a LOT of heat!). It doesn't leak, and even if it did, it could be repaired. No more ally for me.
Mike Howlett


you can pick up a good quality new cross flow rad for 72 from Welsh MG or he may have a good s/h vertical rad if you want to stay original.

Jeremy Tickle

Like Onno said ive got an alloy rad in my midget.
Got the first from a wellknown spridget supplier and it was rubbish, started leaking on 2 places within 2 years: unfixable...
Had one custom made here in Holland and it has been fine sofar until now(5 years later).
I seem to have a leak around the small pipe over which the hose goes, changed hoses from silicone back to rubber but still suffering.
As we speak the radiator is coming out and will be pressure tested to see if its in the rad.
If not ill probably have the hose-pipes changed to make the hoses fit thighter.

A weird coolant leak I tell you...
No one ever said modifying was simples. :)

A de Best


It sure looks well crafted, have been able to actually find the leak

Currently im running straight water.with a bit of water wetter for another 300 miles...I was thinking adding food coloring just incase of a leak but I never got that far, might help you though.

Prop and the Blackhole Midget

the few times I've seen s/h parts on ebay from Welsh MG the parts have looked a bit scabby and with high price tags - I'm not saying they were scabby as I don't know but they looked it, but certainly the prices were high

perhaps I've only seen an unrepresentative sample
Nigel Atkins

Something also to consider about aluminum rads that we are talking about

How many are an exact replica to the orginals... probably not many, mine sure thats probably where the extra claimed efficiency is.

On mine it hold just over a gallon of fluid, it circulates the fluid twice before putting it back in the engine, the piping is much bigger, the heater hose goes to the rad and not back into the top hose just before the water pump, ive elminated cross flow pipe, plus im using the 1500 shroud, because its much thicker and the rad is considerably bigger and takes up a large chunk of space at the maybe aluminum is not as heat transferable... but ill take my rad over the lucas 1275 rad any day

I think thats the real advantage of the new aluminum rads, they designed a little differantly then the old lucas,

im just sorry to hear so many are having reliablity issues with there new aluminum rads... im glad I went the extra few dollars and had mine custom made by professional race car silicone in mine.

Arie... im hoping you can get yours sorted, its looks really well made it has to be something very simple...a pin hole or something along those lines

Prop and the Blackhole Midget

Interesting point Nigel.
When the Midget went back on the road in 2008, many of its parts were new, including the flasher unit. It lasted, as did its new replacements, a couple of months before burning out.
Exasperated I approached Phil at Welsh MG and he kindly sent me three used flasher units from the cars in his yard. All were well used, pretty rusty and well, scabby. I installed the scabbiest one and it's still going strong five years later...
Jeremy Tickle

scabby appearance is less important on some parts than others

on parts where the appearance is more important then the price normally reflects the amount of additional work the buyer has to put in to get them to look reasonable

but if they have the market price right because their items sell then it's me undervaluing the items or was just lucky at those times to see better looking items for less elsewhere

and I have to allow for their business overheads too

so - fair enough
Nigel Atkins

I had problems keeping the temp down on my crossflow in my autocross car. ( '70 with 1275) I had it recored at my local shop with oversized cooling tubes. My temps dropped 20 degrees. Wasn't cheap. Don't remember how much but well worth it. Looks original and no leaks.
J Bubela


Have you decided what you are doing? Where did you get your quote to fix your own?

There's an old boy lives not far from me, who's been working or rad's for 30 plus years. His w/shop looks like something out of a museum. Works on loads of old stuff. Might be worth a quote to see if he's cheaper.
Lawrence Slater

J Bubela, Connecticut, USA

Are you certifiably nutz !!!

You gave my point validity.....who does that here on this forum, you can think it, but your not supposed to actually ever admit to it !!!

It must be an american thing


Prop and the Blackhole Midget


You tried asking a radiator repairer to quote for rebuilding your existing radiator with an uprated core? This is a common thing to do for racing Minis with original side mounted radiators (putting in a 3 core [row] radiator to replace the existing standard 2 core radiator) - Midget racers out there, is there room for a slightly thicker radiator?

If so try a local radiator rebuild shop. You could also try a branch of Serck Marston:


PS before spending lots of money, back flush your rad and heater and make sure hoses are all good, put in new coolant mix
M Wood

Yes, I run a crossflow rad in the racecar - rebuilt with a 3-row core.The rad shop I use should be convenient for Josh, it's in Farnham.
David Smith

Yepp... if its real thick you can use a 1500 shroud.. plug and play direct fit
Prop and the Blackhole Midget

This thread was discussed between 06/05/2014 and 12/05/2014

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