24T2 carb

[Tony Griffiths]

Desperate for a Zenith 24T2?
You can buy a new one, reviewed here: https://www.youtube.com/watch?v=MdvrQc4UiSE
It's a rather over-long and rambling explanation but interesting.
Several suppliers are active at prices that vary widely: https://www.amazon.co.uk/Seroon-Carburet...2624&psc=1
The correct jets might be available from: http://www.villiersparts.co.uk/zen.html The company can also provide, on an exchange basis,  completely rebuilt, "as-new" units. I have one on my car and it works flawlessly.
Details of jets here: http://www.da7c.co.uk/technical_torque_a...ettor.html

[Ruairidh Dunford]

I ran the RN on one of these over 60k miles, it would return about 48mpg.

Can you tell me what jets you fitted, please?

[GK5268]

I have recently fitted a brand-new genuine Zenith 24T2 to my Swallow and had to source the correct parts as specified for an Austin 7.

Carburettor Hospital supplied the specified main jet of "75", don't know what his stock levels are like

https://www.carburettorspecialists.com/

Gower & Lee did have the correct needle valve of "1.5"

http://www.gowerlee.dircon.co.uk/

but no longer have the air jet, this seems to be difficult to get now, I think I had the last one of their stock

These people have the slow running jet "50"

https://www.lsengineers.co.uk/zenith-24-...parts.html

and other spares

This eBay seller has the 14mm choke

https://www.ebay.co.uk/sch/i.html?item=1...owercutter

As said in the above posting, brand-new complete carburettors are available, either genuine Zenith (i.e. Burlen) or a knock-off chinese copy, tractor suppliers should have the genuine item, and are more expensive but the real thing, easy identifier are the screw fixings, genuine have the slotted, chinese have a cross-head... These new supplied carburettors will need to have the jets, choke, etc., changed to suit the settings for an Austin 7.

I have done around 1,200 miles on my 24T2 so far since fitting a few months ago, it is much easier to start from cold - first press on the button and it goes, and on long runs (200 mile journeys of hard driving), I managed over 50mpg average, local driving less so.

I got fed up with the bronze 22FZ mis-behaving (which is wrong for the year of my car anyway), it was unpredictable with its fuel leaks from the needle valve with the engine stopped (would be perfect, then next time, not, parts changed, new old, made no difference, was unpredictable) and was difficult to start from cold, needing about 6 or so turns with the starter motor, before it fires up.

The only issue I have with the 24T2 is that I don't seem to get full engine power on a wide open throttle under heavy load, it seems to hesitate everso slightly momentarily, like it is gasping for fuel, but not always the case, if it is doing hill climbing, it will feel like it is a short of fuel, then catch up with itself, gasp again, and so on until the climb is complete! But not every time!

I did wonder if fuel flow from the tank was insufficient, but filling a pint milk bottle (0.5 litre) took around 40 seconds, I can't imagine circumstances that the car would ever consume that amount in such a short time, so that is not the issue.

I have just swapped the new needle valve for another new one and I think this has improved things, I have only done about 40 miles on the less hilly side of my route westwards out from home, so too soon to say, eastwards is hillier and will be more apparent when I next go in that direction if this is cured or still present.

I did wonder if the fuel was vaporising and I have a temporary fuel line, which is clear plastic so I can see what is going on, and I introduced a breather pipe to see if that would make any difference, it didn't.

I don't recall this issue with the bronze 22FZ, I might just swap it back as a test in case I mis-remembered!

[Ruairidh Dunford]

Fantastic detail, Gary, thank you very much indeed.

[Tony Griffiths]

I ran the RN on one of these over 60k miles, it would return about 48mpg.

Can you tell me what jets you fitted, please?

Hello Ruairidh - just the standard jets:
Main 75
Slow running 50
Air cap 150
Choke tube 14mm
I had a well-used one on the car in the 1960s and 1970s and, like yours, it would do from 40 to 50 mpg.
The new carb gives much the same.

---

I ran the RN on one of these over 60k miles, it would return about 48mpg.

Can you tell me what jets you fitted, please?

Hello Ruairidh - just the standard jets:
Main 75
Slow running 50
Air cap 150
Choke tube 14mm
I had a well-used one on the car in the 1960s and 1970s and, like yours, it would do from 40 to 50 mpg.
The new carb gives much the same consumption, starts instantly, idles at 2 r.p.m. with the transition from tick-over to power is entirely smooth.
The only drawback? They really don't look the part!

[Alan]

No, the VSCC objected to mine at one stage. I tried a choke tube bored out to 16mm. Top speed was higher but mid range it suffered a bit.

[Ruairidh Dunford]

Thanks, Tony.

[Steve kay]

No, the VSCC objected to mine at one stage. I tried a choke tube bored out to 16mm. Top speed was higher but mid range it suffered a bit.

The VSCC objected to something relating to an Austin Seven? I am shocked, I tell you, shocked! Now under the new regime if it had been a TR2 or a Swallow Doretti everything would have been fine.

[JonE]

I've got a 19mm choke version new old stock to fit to the Gould Ulster with a reversed downdraft inlet and a repro Ulster exhaust; with a variable main jet. Been interested to hear Gary's findings...