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MG Midget and Sprite Technical - 1500 manifolds project - something a bit different

Hi folks,

As you may have figured out from a few other threads I am working on a couple of concurrent projects in a bid to better the breathing capabilities of my 1500. I thought it may be of interest to people.

I should say from the outset, yes, I am aware this could have been done so much easier with an off the shelf Peco tubular exhaust and a set off SUs. But it is one of those things that just sort of snowballed in one direction. Plus, as I am currently out of work, I am rich in time but poor in money, so this was (a little) cheaper than buying a whole load of new parts.

The basic problem was that the inlet manifold I have for the DCOE fouls on anything but the standard exhaust. I had a second hand tubular, I butchered it trying to get it to fit and I gave up and re-fitted the standard exhaust (that was about a year ago now, before the car hit the road).

By chance I happened upon a Spitfire 1500 manifold for a tenner and I hoped this would fit. Sadly not, the 1500 Spitty manifold is as bulky as a tubular item. But as I now had it, I figured I would work with it and also modify the inlet manifold.

Pic of the clashing issue with Spitty 1500 exhaust and "old" inlet manifold.

Malcolm Le Chevalier

and the standard midget 1500 manifold vs. the Spitfire one, showing the difference in depth.

Malcolm Le Chevalier

So anyway, I am in the process of extending the inlet manifold to give me more clearance. Something a bit like this...

Still practicing my aluminium welding though!

Malcolm Le Chevalier

In terms of the exhaust manifold I have done two things:

1. Removed the brackets to which you bolt the inlet and exhaust manifolds together with on a standard Spit/Midget. This was to try and give me a bit more access for doing up the lower manifold nuts.

The problem with this is the brackets aren't solid... doh! I cut one off and was left with a hole! I welded this up with a bit of plate.

Pic of holes after cutting off brackets...

Malcolm Le Chevalier

the second thing I did was to put a "baffle" into the middle runner.

Like with the Midget manifold, the Spit manifold has a Siamesed central runner. I sliced down the middle of this, slid in some metal in and welded it up again. The idea being it will stop the two exhaust ports interfering a little bit. Whether it actually does anything in reality... well, who knows!!! It is only two or three inches long.

(I need to tidy up the flange on this)

Malcolm Le Chevalier

I also repaired/helicoiled the stud holes and matched the ports to the manifold gasket.

This pic shows how much one of them was off by (the other ports were the same). I just attacked it with a dremel!

Malcolm Le Chevalier

After... (you can't really tell the difference, I forgot to photo it with the gasket again!)

Malcolm Le Chevalier

On the dual spitfire downpipes there was some pretty nasty welding...

Malcolm Le Chevalier

Which I also dremel-ed off to smooth/increase the flow a bit.

Malcolm Le Chevalier

Finally, I put in a lambda probe port in each downpipe. This will allow me to get a lambda reading for each carb barrel (due to the cross over manifold).

Also a lick of paint on the manifold.

Malcolm Le Chevalier

I need to tweak the chassis a bit to get the exhaust to fit and wee bit of work to link it up to the current exhaust. A new rest of exhaust is a project for a later date.

Also need to finish off the inlet manifold.

Hope this is off interest to people.

Comments welcomed. Hope you enjoyed the pics and don't mind reading the many posts.

Malcolm Le Chevalier

What are you using to weld the cast iron manifold welder and alloy wise and how are you finding MIG welding aluminium. I've had my MIG welder about 30 years now and had the stuff to weld aluminium almost as long but have never used it as I acquired an AC TIG add on for the oil cooled welder not that long after getting the aluminium MIG kit.
David Billington

Not bad malc...

i played around with making an inlet manifold several years back ... they can get very involved quick as you have found out

keep at it
Prop and the Blackhole Midget

Good little project you've got going there Malcolm
With the aluminium welding, of which I know very little---- There is a bloke that goes around the shows here selling aluminium welding kits for torch welding'
He welds drink cans together as part of his demo
He told me to never use a mild steel wire brush for prep. work as it plays up with the welding process
He always uses a stainless steel brush
Looking at the quality of his welds I'd say whatever he says is worth doing--might be worth a try if you're not using one already
William Revit

Willy, The guys doing those demonstrations are slick. They make everything seem so effortless. Were you watching a demo of the Henrob type torches?
Trevor Jessie


I expect it was a lumiweld type demo as the Henrob torch demo is just OA aluminium welding and uses a flux although a clean with a SS wire brush wouldn't hurt.
David Billington

the cast iron I just welded with steel MIG. I heard stainless wire works better on cast iron, but I couldn't be bothered setting it up! it was a bit of a git to get it started, my MIG doesn't really have the beans until the part is warmed up a bit, maybe I should bake it in the oven or something!

aluminium MIG is a bit tricky, again, have to bake it in the oven for ten mins before welding or it doesn't penetrate.

Ali MIG is a bit scruffy, but nothing a grinder won't fix!

hope it is strong enough :-/

Malcolm Le Chevalier

I tried welding a cracked 1500 exhaust manifold once but just couldn't get the CI to form any sort of weld pool. It seemed to just go direct from solid to "hole" in a splatter of sparks. If I did get some weld to form at all it was just sat on the surface with no proper bond with the CI. I gave up and bought a new tubular manifold. - Hats off to you Malcolm for getting that welding to work!

I've tried welding a couple of CI manifolds using an arc welder and CI rods, with varying results.

I believe you are supposed to get the CI (red?) hot first. I didn't have any means of doing that, so tried heating with a blow lamp, but it was quite a large lump of metal to try and get hot. I dare say it was barely warm!
Dave O'Neill 2

Well... I don't know how strong it will be, but as long as it is air tight it doesn't need to be that strong I suppose?

You do have to grind down to nice shiny metal, any rust pitting and it will just spatter everywhere and not stick.

Malcolm Le Chevalier

Dave O'Neill is correct I think. The trick to arc-welding CI is to preheat the work to red hot if you can, but it should be done evenly, not locally with a torch. The whole workpiece should be at the same temperature, to minimise the chance of stress cracking.

I did it years ago to repair a flue collector box for a cast iron range. I just remembered I still have some of the electrodes squirreled away if anyone needs some.

At the time I had a coal stove in the living room so I put the collector box in the fire and did something else until it was glowing red, then set it on fireclay bricks on the bench and welded it up.

David B is also right I think about the Lumiweld process. This is highly effective, but the kits are not cheap IIRC. I repaired a broken mounting flange on the carb from a prewar motorcycle with it, with my heart in my mouth as the owner told me it was irreplaceable! I've also done LandRover body panel repairs with it. As Willie implies cleanliness is the ticket. Ally grows a thin "skin" of oxide very quickly when exposed to air, which then protects it from further corrosion. At least that's my understanding. That "skin" needs to be broken and cleaned off using a St/St brush immediately before welding. I'm not certain that Lumiweld is a true weld in the sense of a chemically fused joint. I think it's akin to brazing but a hell of a lot easier. As with any ally welding anything more than about 3/16" thick benefits from preheating the work. I can't remember the proper temperature, but I bet Google knows! As a guide I used to preheat until a small piece of clean white pine scrap would just char a litle when rubbed on the metal. Not very scientific, but it worked for me.

As an aside my Old Man was a superb welder and his party-trick for a bet was to weld together the ally foil from cigarette packets with Oxy Acetylene gear. I'm not bad, but I was never that good. I know how the trick was done, but I never managed to repeat it!

Malcolm, my hat is doffed to you for your inventiveness. Well played, Sir!

"and did something else until it was glowing red"

Really !! Too much detail Ron!

Haha Guy!!!

A gentleman never tells.........


Red? only red?
If it doesn't get purple your not trying hard enough. LOL!!

I need to get this project finished this week. Not having my car on the road is seriously depressing!
Malcolm Le Chevalier

Regarding the low temp alloy welding,I purchased some about twenty ,twenty five years ago when it first came on market. I used it to a repair on a piper arrow door. They were known forever cracking. I welded it up and also a fillet for strength and it never went again.
It's great stuff but since I bought a tig I've never used it again. By coincidence I was talking to the guy pushing it at the restoration show last weekend
S E Bond

Update on this project:

1. Spitfire down pipes are a pig to fit. Not only due to the proximity of the chassis rails, but the dimensional quality of them is crap and they can foul on the sump and gearbox as well. I doubt the pipes I have would even fit on a Spit!

2. MIG welding is the incorrect tool for Ali. All I made is a mess. In my defense, a manifold is a pretty difficult shape to start with I suppose.

After two weeks, I give up. I bought a new inlet manifold and I am going back to the standard exhaust system as I want to have a car to drive.


Malcolm Le Chevalier

This thread was discussed between 01/03/2016 and 10/03/2016

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