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MG Midget and Sprite Technical - 45 Weber upgrade?


Someone on this forum recently was asking for views on switching from a single 1 3/4 inch SU to a 45 DCOE Weber twin choke side-draft carburettor.

Did they do it. If so, how did it go?

M Wood

Morning Mike - I think that was me....
I've got as far as buying the Weber, the inlet and the K&N. To be perfectly honest, I haven't fully decided whether to go ahead with the conversion or not yet. If and when I do, I will post here how it went ;)

Are you thinking of doing the same?


Glynn (1275RWA) Williams

good afternoon
if you are not a purist, as I am not, fit the weber
I replaced twin su on a 1500 with a 45dcoe with all the correct jets etc...just bolt on and go.
no balancing or sticking needles.
you may need a fuel pressure regulator..webers run on lo pressure.
I would go for he weber every time
If you can remember the early 70s pre efi, almost
anything with clout had one or more webers, all the fords some Vauxhalls and the quick chryslers/Hillmans
that is my opinion for now and my very quick viva of the late 60s/early 70s
I am sure someone will shoot me down in flames ?????
rgds tony
a boyle

But whatever you do, don't fit those clutch plates.

I know, I know, some people swear that webers go better with a clutch plate or two in the system, but trust they don't

And I wouldn't spray the lot white either.

Lawrence Slater

Thanks Lawrence for the advice re the clutch plates - couldn't work out whether they went between the carb and the manifold, or the carb and the K&N....

Meanwhile, the white paint is actually filter cleaner ;)
Glynn (1275RWA) Williams


What's the orange rectangular looking object, and what are the shiny tubes?
Lawrence Slater

the tubes are stub stacks
G Lazarus

I did a back-to-back rolling road session a few years ago at a certain garage in Croydon (Paul ?).

The SU HIF6 delivered 102 bhp, with a K&N filter in a Metro air cleaner box, and with the Weber 45 it was 106 bhp with an oval K&N.

Since then the cam has been changed from a Kent 276 to a Piper 270 and the HIF6 has gained a stub stack and K&N circular filter - power is now 112 bhp - no Weber comparison this time.

The Weber is overchoked at 38mm, and does nothing at <2,000 rpm, and then goes very well, and sounds lovely!

Overall the SU is much nicer to drive in day-to-day traffic, but maybe some 36mm chokes in the 45 would make that as good as well?

Richard Wale

Thanks for the extra info.

Things must be REALLY quiet at the moment! The orange rectangular thing is actually the filter cleaning fluid (the white aerosol is the filter oil)

Glynn (1275RWA) Williams

Ah right Glynn.

Shouldn't be that quiet. I should be more often in my garage, sorting my oil sucking engines. I'm building up to it. lol. I did some tests yesterday for an hour or so, and today, I began to grind in the valves on my spare 1300GT head.

Plenty to do really, just a lazy bastard who can't get his finger out. lol.
Lawrence Slater

are the orange rectangular filter cleaning fluid and white aerosol filter oil alternatives to K&N brand as I can only remember them in black boxes and bottles - but I have a poor memory and some alternatives might be just as good

a mate of mine used K&N cleaner and oil on a foam filter thinking it was a K&N, probably just as good as the proper (other) branded stuff
Nigel Atkins

Nigel - they ARE alternatives (not K&N). The seller threw them in with the package so I took them. I hasppen to have plenty of original K&N product so will be using that first...
Glynn (1275RWA) Williams

cheers Glynn, not that often I remember right
Nigel Atkins

This thread was discussed between 14/12/2014 and 19/12/2014

MG Midget and Sprite Technical index

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