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MG Midget and Sprite Technical - Dented Exhaust

MkIV, 1275, Maniflow LCB, Weber DCOE

Doing routine checking and adjusting,I found that plugs 2 and 3 were slightly sooty whereas 1 and 4 were about the right colour.

After a spot of head scratching, I decided that, as there is no balance tube between inlets, the only factor creating those pairings must be the exhaust.

Delving underneath, I discovered this dent and decided it must be restricting the flow, making 2 and 3 richer. However, I now realise that the dented pipe serves 1 and 4.

I was intending to book a rolling road session but I'd like to get rid of this dent first. I have an idea how I might approach it, but has anyone here tackled this sort of problem successfully?

I can't recall any significant bangs or knocks when out and about; I can only assume it happened when I spun out across a rumble strip at Harewood. There was quite a lot happening very fast so I wasn't listening particularly carefully, and, anyway, I clouted a flip-flop marker at the same time.

Colin


C Mee

Difficult to tell how deep it is from the photo.

Option 1: weld something to it in order to pull it out.

Option 2: cut a flap, open it, straighten it, fold it back and weld it up.

There are probably other options.
Dave O'Neill 2

Yep. There's option 3.

Send it to me, I need a new one too.

I'll fix it with one of Dave's options, you buy a new one. 😁





anamnesis

Self tapper into the deepest part of the dent. Pull it out. Weld up the tapper hole or remover self tapper, cut the pointy end off and refit it, sealed with a little gun gum.
GuyW

Yep, as per Guy, self tapper dead in the centre, heat the end portions of the crease and give it pull out with a slide hammer, then reheat a bit closer in and pull again working your way towards the centre---pull the screw out and weld the hole up- It doesn't look bad enough to be worrying the mixture much though.
Having different colouring on the plugs 1/4--2/3 is typical of a weber, specially if you have an upgradaed cam and the bigger the cam the bigger the issue
On my old racer with a 320deg cam it would idle on 2 cylinders only, you could pull 2/3 leads off and it'd make no difference to the idle running.
Up to about 1500/2000 rpm normally before you could hear them starting to catch on--it's all because of the 2 inlet port setup.
David Anton(rip) from Aptfast did a LOT of research on this and invented the scatter patern camshaft to help overcome the 2 port airflow problem.
You've probably just had it idling too much or just puttering about maybe.If you give it a good blast up the road the plugs should clean/colour up ok.

willy
William Revit

Thank you for your suggestions, especially to you, Willy, for your explanation. I wondered what folk were on about when the talked about scatter cams.

Seeing as the dent probably isn't upsetting the mixture I'll add the job to the winter To Do list.

Thanks again
Colin
C Mee

This thread was discussed between 10/07/2024 and 11/07/2024

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