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MG Midget and Sprite Technical - Radiator cowl. 1500vs1275. What's the difference?

This refers to the later type cross flow rads. The purpose is for changing from vertical flow to cross flow rad. Hence the need to obtain a cowling.

What's the difference between the 1500 rad cowling vs 1275 rad cowling?

They have different part numbers, so I guess there is a difference.

Could a 1500 cowling, be used to replace a 1275 radiator cowling directly?

If it needs a mod, what needs changing?

Lawrence Slater

I think the 1500 one is shalower to account for the longer engine, moving the rad forwards slightly. I also think the holes for the rad bolts are different. It's been a while since I tried this.

They are different though and it's not just a parts numbers ploy. I think you'd struggle to modify one for the other, might even be easier to fabricate from scratch!
Roadwarrior

The cowling is different but easily enterchangeable between the 1275 and the 1500

The 1500 shroud moves the radiator about 1.5 to 3 inches closer to the grill (I cant remember the exact measurement) which is great if your going to use an electric fan instead of the fan in the engine

But ... using a 1500 cowling for a veritical rad.... thats going to require some mechanical engineering creativity is my guess

Prop
Prop and the Blackhole Midget

CROSSFLOW RAD Prop.

I want to fit a crossflow rad, and need a cowl.

OK. So if I've understood this. The 1500 cowl is shallow compared to the 1275 cowl. Hence the standard pump driven fan would be less effective if I used a 1500 cowl with a 1275 engine.

Bummer. The 1500 cowls sell for less than the 1500 cowls on ebay.

Guess then I'll have to shell out more for one then.

Unless someone has a spare they want to sell me 'cheap'. :).

Thanks anyway Road and Prop.

Lawrence Slater

Is the WIDTH and HEIGHT, of the 1500 cowl, the same as on the 1275 crossflow cowl?
Lawrence Slater

Lawrence, the height and width are the same. It bolts directly to the rad. supports and the rad. bolts up directly to the cowl. As Prop said, only the depth is different, about 1.5". That will allow you to put a slim puller fan on. If using the mechanical fan, it will be about 1.5" further away but I don't know how significant that would be. You could do a little scientific test for us! Don't know how difficult it would be but you could make a shroud that would probably make it more efficient than stock.
Jack Orkin

Here is a picture of the two for comparison. One other difference, the 1500 one does not have the captive nuts on the bottom piece that coincides with the slots in the piece behind the grille but they are not really needed.


Jack Orkin

Thanks Jack, that helps a lot. :). I can easily alter a 1500 one then. Cheers.
Lawrence Slater

I think I may have a 1275 one somewhere.
Dave O'Neill 2

How much Dave?
Lawrence Slater

I don't have a usable spare Lawrence, or would have offered.
David Smith

With the air flow in the engine bay so robust for the midget the 1.5 inches wont make any differance

If anything it will make it easier to get your tie sucked into the spinning fan blade

You will be safe with little to no differance between the two, or im going full trans also.

Prop
Prop and the Blackhole Midget

Mine was fairly bad, so I fabricated some replacement sections from sheet steel as they are only simple folds and square - cut it apart and welded them in.
Replacement captive nut casings are available from Moss etc.
So if you can get hold of a knackered one as a pattern it is a fairly cheap option - especially if you can salvage some of the bits.
richard boobier

Thanks David. No worries.

I mught do that Richard, if a good 'cheap' one isn't available. I do have a pattern, as I have a '73 Midget too. So I guess I could just copy the cowl from there.

But now I know that the height and width of the 1500 version is the same, and as Prop says, the depth probably won't make much difference, it may be worth me seeing if I can pick up a 1500 cowl cheaper. Then if I need to, I can just extend the top and sides a bit..
Lawrence Slater

Bought a good clean 1500 cowl on Ebay for 16 quid inc postage. I'll try it in my Sprite without modifying it first. If it cools ok, cool. If not, I'll extend it.
Lawrence Slater

I converted my '66 Sprite from vertcal flow cooling to crossflow cooling yesterday.

I used the 1500 cowl unaltered.

I can report that it works a treat. No need to move the radiator closer to the fan. Pretty hot yesterday, but even hammering it up a hill the temp stayed below 160, -- I'm running without a stat as an experiment to see how well the xflow rad cools, compared to my old knackered v/flow rad.

Anyway. 2 distinct advantages from using a 1500 cowl.

1). They are cheaper on Ebay, than the 'correct' 1275 cowl. Money's always a factor with me. :).

2). And this the best reason to convert. Quick release rad straight out of the box.

Because the 1500 cowl isn't as deep as the 1275 cowl, to remove the radiator, all you need to do is release the top and bottom bolts on the radiator. Because there is less metal on the top of the 1500 cowl, the rad simply tilts forward, and lifts out. No need to bend, or alter the top of the cowl. Acutally, rather than bolts in the bottom of the rad, I have again replaced those with locating studs. Hence to remove my rad, all I have to do, is drain -- from my special drain tap -- , remove the top and bottom hoses from the rad, remove the two top bolts, and the rad lifts out.

I'll probably fit a bolt on extension cover to the top of the cowl, using the existing 2 bolts. I'm not concerned about finger protection, but I don't fancy an eyeful of whatever, thrown in my face if happen to be leaning over it, when something gets thrown up.

PS. You won't find this in books or user manuals. Nod to Guy. lol.


Lawrence Slater

Out of interest Lawrence why have you changed to cross flow? Is it that you just happened to have one lying around or another reason?

Trev
Trevor Mason

Hi Trev.

Multi part answer.

1). I bought an rwa Midget. I was impressed with the easier access to the front of the engine with the x/flow rad.

2). When I was getting the rwa back on the road, I modified the cowl to allow for very quick removal of the rad. This can't be done as easily with the v/flow rad.

3). I've been removing and re-fitting my '66 Sprite engine and v/flow rad, for experimental purposes. It's not hard to remove and refit the rad, but it's time consuming/fiddly compared to my modified rwa.

4). My v/flow rad is the orignal 1966 item in my sprite. It's knackered. A new v/flow rad is more expensive than a x/flow rad. I was able to buy all I needed to convert, including the cost of a replacement x/flow rad, for less than the cost of a new v/flow rad.

5). Minor irritation. You hardly ever need to top up an x/flow rad due to the expansion bottle. You can, and I did, add an overflow bottle to my v/flow rad, but it's not as efficient as a sealed expansion system. -- at least mine wasn't, and the rad was f*cked anyway.

I liked the look of the old v/flow rad header, but I always prefer function over form, and now I have it.

Lawrence Slater

I'm impressed by x/flow rad I've converted too.

I didn't have a cooling problem with the vertical rad in my Sprite. But it was old and showing signs of leaking, -- water stains, but no actual drips or running coolant.

With the v/flow rad, the engine would always run at over 150f, even in the winter. With the x/flow rad, if I don't put a stat in, even in this hot weather, I can't get the temp over 160f.

I assume that points to my v/flow rad being at least partially clogged, although I pressure flushed it forwards and in reverse. Or, are the x/flow rads simply better at temp control? -- I've noticed that the my rwa Midget (x/flow rad), runs very cool too.

Either way, the x/flow rads must be more efficient, since the coolant capacity is one 3.4ltrs in the x/flow, compared to over 5ltrs in the v/flow rad.

Lawrence Slater

Hi

I am reviving this thread for someone who is fitting a 1275cc engine and vertical flow radiator into a 1500 shell and and having clearance problems with the fan; sounds like from this thread it is a fan shroud problem due to different depth of shroud between 1275cc and 1500cc models and a need to switch to a crossflow radiator? Is there anything else they need to look out for? Guess this is a potential problem when people fit a 1275cc engine into a Heritage replacement shell as that is 1500cc based so need a 1275cc fan shroud?

Hopefully my friend will join the BBS and ask what they need to know. In the meantime any 1275cc shrouds about please and sources of good Crossflow radiators? (Guess a good secondhand rad and getting it checked/recored is the way to go)

Cheers
Mike
M Wood

I should read the BBS more carefully! Russell has posted a question about this a few days ago under ‘Cooling Fan’
M Wood

This thread was discussed between 04/06/2015 and 10/06/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.