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MG Midget and Sprite Technical - welding a cast manifold

Evening all,

Has anyone ever, or does anyone know if you can weld a cast iron manifold, such as the exhaust manifold on a 1500? Using a MIG welder?

Cheers,
Malcolm
Malcolm Le Chevalier

Malcolm,

No it can't be done with a MIG welder with any reliability, although I do wonder if you have the facilities to preheat high enough before welding and slow cool after that you could increase your likelihood of success. You may be able to TIG braze it or use a high nickel rod intended for welding cast iron with a stick welder or oxy acetylene welding and a cast iron filler rod and flux. In any case preheating and slow cooling after welding will help achieve a successful result. I have repaired CI with high nickel rods and stick welding successfully but have also seen a welding instructor repair CI unsuccessfully with MIG and wondered what he was thinking.
David Billington

No.
Possibility that you could if you heated the manifold red hot in a fire, welded hot, let cool very slowly (24 hours ++) while wrapped in insulating blanket, or the ashes, if you have a lot of ashes. Not worth it, except as a scientoofix spearamint.

FRM
FR Millmore

Hi Malcolm

If you use stainless wire with your MIG you can get some penetration into the cast iron. However it is a slow process, weld a tiny amount say 1/4" and then use a chipping hammer to stress relieve the weld as it cools and try and prevent cracking. We have used this with 100% success rate to repair heads burnt away between chambers and blocks burnt between cylinders. The easiest 'home way' is as David says, use a high nickel content (99%) rod in a stick welder, they are rods developed for cold welding dissimilar ferrous metals on site. Again small weld then lots of stress relieving as the weld cools and look for surface cracks after and be prepared to reweld and reweld and reweld.

Peter
Peter Burgess Tuning

Postage on an e-bay purchased one would be cheaper.
Or take the opportunity to justify purchasing a performance manifold as a replacement. ;-)
Guy Weller

Thanks all, yeah been reading into it a bit more this morning.

Basically I was having a bit of a Prop moment. I want to replace my standard exhaust manifold as, as everyone knows they are pretty rubbish due to the joined middle ports.

I looked at 'proper' tubular manifolds. But at circa £150 - £200 I was put off a wee bit.

The 1500 Spit manifold still has the joined middle port, but I think is still better. But then I need to get a down pipe and this is apparently a bit of a weak point. And it won't fit onto the midget exhaust (as far as I am aware) without messing about.

The 1300 Spit manifold splits the middle ports but has a different joint to the down pipe and at a different angle so I would still and have the same problem with fitting the rest of the exhaust.

So I wondered if the standard Midget manifold could be modified to split the centre ports and whether this would give any noticeable benefit? The idea in my head last night was to slit the manifold down the middle, slide in some steel and then weld it up.

The rest of my exhaust system is in OK condition so could be reused as it would still fit as normal.

But just been out to my garage this morning and had a proper look at the manifold I have. It appears to have been repaired previously (see pic) and isn't in that good a nick. Therefore I might mess around with it and if it all goes wrong it will force me to buy a tubular manifold... hmmm.

Peter, if you are still there it would be good to get your thoughts on 1500 exhausts. Engine is +40 thou, K and N, all balanced and with a Piper 270 cam.

Thanks for reading all.
Malcolm




Malcolm Le Chevalier

TIG brazed a cast manifold last year. Worked really well. Can't remember if it was a random silicon bronze or some SIFBronze Number 8 rod that I recall buying in for something special. Anyway, it worked a treat.
r thomas

I use Sifphosphorbronze no. 8 for TIG brazing.
David Billington

This thread was discussed between 09/03/2013 and 10/03/2013

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