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Apologies for all the questions but clearly, I'm new to the Herald.

I'm pretty sure this is not an original carb so, if it's not, what's it from and what's the white plastic doofer on the side?



The car still runs from a choke cable so don't think it's any auto choke device.

I thought the car was running a little rich but can't see how to adjust the mixture on this as there's what looks like (and I can only see it by photographing it) a castelled type nut on the bottom (last pic). Don't really want to take the carb off to get a better look.

I've got three other carbs that came with the car and they all appear original, (i.e with the jet adjusting nut on the bottom and no white plastic doofer), so are they much of a faff to strip, clean and set up because if not, I might stick one of those on.

Car seems to tick over fine and the plugs are nice and sandy coloured but others commented on it running rich and it did seem a little towards that end.


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That looks like a late Stromberg 150CD. It's not the right one for a Herald 13/60 but it's quite similar. The big differences are:
- the white plastic capped long doofer on the side. This is a thermostatic correction valve, similar to the waxstat on late SUs.
- the nasty late Stromberg tuning method requiring a special tool inserted down the dashpot damper hole (and likely to rip your diaphragms if misused)
- possibly (though I can't quite see from your photos) a weird circular enrichment valve for the choke

These carbs were fitted to a lot of cars in the early '70s, including Mk3 GT6s (where there is a pair, only one of which has the choke unit, the other relying on a balance pipe).

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these are CDSE or there abouts  the white thingy is a temperature compensator that is supposed to  open a air bleed to bypass the throttle plate and increase the idle a little and weaken the mixture when in hot conditions  they are now aged and often open when should be closed

  take out the two screws and have a look
the part which goes inside the carb body has two o ring seals one at the head of the round and one to seal this with the bore bottom

both become degraded and will let air in .

remove the plastic cover reveals the bi metal strip and a small plunger , never mind what the manuals say this little sod needs to be closed for normal running or you never get the idle mix right
simple turn the small nut till the plunger is sprung 'closed' and give it one more turn.  if it never opens its not really a problem

you just dont want it open when it should be closed is the most important clue.

the carbs will also have a small hole in the manifold gasket to pass this air bleed into the manifold,

adjustment is by a long allen key down the dashpot tube, there is no adjustment from the underside
some of these have an offset slot which needs special tool or care with a screwdriver (not normally on triumphs)

when adjusting the needle either take the piston out and hold it  or get the special tool which has a knurled  knob  to stop you rotating and tearing the diaphragm.

hope that helps a bit


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Thanks for that Rob.

So, do you think the thermo CV is doing anything on mine?

Don't fancy the potential tuning disaster!

Could be EV for choke.

Is it worth sticking one of the originals on? As stated, it seems to run OK so I might leave well alone unless some problem manifests.


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Hi John,

I think Pete answered the thermo CV questions pretty fully :)

I would say, having a Mk3 GT6 (late type Strombergs) and a Mk1 Vitesse (early type) in my garage, I'd leave it alone if it works but consider putting it back to original if you have one spare. I've rebuilt both types and, while there's very little difference in their performance when working, the earlier ones do seem a lot less hassle.


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