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MG Midget and Sprite Technical - Heater Duct Query

The heater intake duct was missing when I bought my Sprite and I have finally got round to acquiring a length of ducting and associated clamps.

Where, exactly does the mid-point clamp mount on the body? I can't find any photos that show it clearly.

The flap valve is also missing from the front panel and is no longer available. Does anyone happen to have one going spare?

Colin





C Mee

I’ll see if I can find a photo for you.

You might struggle with the flap valve, as I think they were only fitted for 1967. Certainly only for a short time.
Dave O'Neill 2

Colin

It looks like my old 1275 had two brackets.

There's also a photo of my last 1500, which only had one. The rearmost one on the 1275 was in the same place, but on the opposite inner wing, obviously.





Dave O'Neill 2

Thanks Dave, those photos are really helpful.

On my car, the screw that holds your clamp is holding a P clip for the loom, which gets in the way. Is your loom secured somewhere beneath the duct or is it 'unattached' all the way through the engine bay?

I'm using aluminium foil ducting as the 'scrute' at Harewood who picked up on its absence told another midget owner that his stock plastic duct wasn't acceptable.

I didn't realise that so few Mks of Spridgets used that flap valve. My Sprite was built in late 1966 and is one of the first 500 or so Mk IVs. If I can get hold of a decent photo I might have a go at fabricating one.

Many Thanks

Colin
C Mee

I think the front bracket shares its mounting point with the loom p-clip. The loom would be above the screw, with the p-clip hole at the bottom.

I'm not sure if the loom was attached anywhere else and I don't own it - or any Spridget - any longer.





Dave O'Neill 2

Snap Colin. My Sprite is a '66 mk4 too, replete with front flap valve.

Only 2 p-brackets. One at the front, and one midway.

anamnesis

I didn't bother with a mid point clamp on the Frogeye rebuild. That's because the duct needs removing to work on that side of the engine and it seems to support itself quite well. No ties to hold duct to intake or heater either.
Bill Bretherton

I don't even bother with the duct.On the Frog I have mounted the oilcooler next to the radiator and use the intake in the bonnet to feed the cooler.. There seems enough air coming through generally to provide an air flow to the heater. I can always switch on the fan if needed.
Bob Beaumont

Thanks for the photos, Dave.

Anam, is there any chance you could take a photo of your flap valve to show the way it's set up?

Bob, I've never been particularly bothered about the missing duct as there has usually been a good enough flow to clear a misted screen. However, I take my Sprite hill climbing and, after 10 years of nobody noticing, a scrutineer at Harewood finally told me off about it as it's absence created a route for fumes and fire to reach the driver.

The same scrute objected to a stock plastic duct on another Midget as that's not fire-proof. He also wanted the rubber fuel filler hose shrouding with something fire-proof. I think he was rather OTT about it but didn't think it worth arguing about.

Colin
C Mee

Colin

Would it not be easier to fit a blanking plate over the front of the blower intake when competing?
Dave O'Neill 2

I can when I get back to the uk in 14/15 days Colin. Meanwhile, I'll try and search the archives. I think a discussion about the early front flap before, led to a picture being posted, possibly by me.
anamnesis

Colin, that scrutineer was being a little cautious!

I think Dave's suggestion is worth pursuing, potentially a lot less hassle.
Bob Beaumont

Here you go Colin. It isn't mine though, I found a discussuon on MGExp.

The way it worked originally, was with a long **solid** inner core cable. You push the heater fan motor switch *in* to OPEN the flap, and pull it *out* to CLOSE the flap. -- The fan isn't on of course, if the flap is closed.

I can't remember if my solid core cable snapped, or if it used to bind/stick. I think it used to stick. But anyway, I replaced it with a flexible inner core. This means whilst I can pull the flap closed, I've had to put a return spring on the flap actuating arm, to open the flap as I push the heater fan switch back in.

See pictures. The red scrawl represents my spring; under tension, as the flap is closed. Pushing the knob back in lets the spring open the flap.

And, it works, happily 🙂. But it would be nicer to make it works as intended I suppose, with a solid core; assuming you could get one.

Or maybe, as I've often thought of trying, but haven't got around to, fit a small electric motor/solenoid to it, --- or something.

Hopefully this will help, if not I post pictures when I get back.









anamnesis

I agree, Bob. I think he was going a bit too far - but very politely so I didn't like to argue.

Dave, for a couple of subsequent meetings I did just that - a Swarfega lid, or something similar, that fitted snugly after a wrap of foam strip on the spigot. I decided I needed the air flow when the lid was in place on a wet hill climb and the screen misted up.
C Mee

Here's the MGExp discusion link

https://www.mgexp.com/forum/mg-midget-forum.3/early-mkiii-midget-heater-fresh-air-valve.4124291/
anamnesis

Anam, thanks for thos photos and link, they're really helpful.

The cable with the solid core has been there all along but it's very stiff to the point of being seized so I might resort to your system using a flexible cable and return spring. Very Grateful.

Colin
C Mee

I reckon it'd be easy enough to make the flap asembly if you can't get an original.
anamnesis

Colin this is listed on Midland Sports and Classic but no idea if they have stock.

https://www.msc.parts/contents/en-uk/d420_1275cc_-_Heater_Fittings_-_Early.html#p14380

Item 14

Rob
MG Moneypit

The metal tube attached to the later heater unit is a separate unit and incorporates the open/closed valve arrangement which is quite similar I think to the one used at the grille area.
May be worth looking at how much work involved in altering one to suit the grille location as I would think there are plenty of donor heater units lying about for later cars.

R.
richard b

That's a good idea Richard.

Meanwhile, if wanting to make one, a US supplier shows out of stock, but has some great pictures.

More pictures here.

https://www.sportsandclassics.com/parts/oem-original-parts/austin-healey-original-parts/mg-midget-austin-healey-sprite-tube-air-valve-assembly-nos/






anamnesis

But why do you need the front flap as the heater has a flap anyway?
Bill Bretherton

Bill, not all Midgets and Sprites had a flap on the heater. There was a year where the flap was on the front panel and consequently these cars didn't have a flap on the heater.

Richard, the heater mounted flap valve is angled to pick up the air pipe which follows the inner wing. It does however have 3 attachment points so could be mounted so as to point more towards the centre of the grille area.

Rob
MG Moneypit

Rob, thanks, I didn't know that!
Bill Bretherton

Rob,
Yes I realise some fettling would be required !!!

However I though that a later unit would yield most of the parts ready made with only some addition tin work required.

ISTR my early 1275 had the vent down there but it was generations ago and memory fades !

R.
richard b

According to Horler's book the heater valve assy remained in the front panel until GAN4 58854, September 1967...Dave
David Cox

When a competition car needs to have a flameproof bulkhead between the engine bay and driver (passenger) compartment it would be compromised by flammable plastic ducting. When the duct has been blanked (on the bulkhead) there is no issue but where it hasn't then I have seen metal concertina type (gas flue?) piping used that meets the regulation but more importantly provides extra seconds of fire resistance when it all goes wrong.

I was NOT that scrutineer at Harewood but I don't think he was going to far, simply advising what the regulations require. You have to have seen how quickly a car fire gets hold to be keener on these things.
Daniel

This thread was discussed between 14/01/2024 and 19/01/2024

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