[Healeys] Thermo Choke Carby Thingy Q

[Alan Seigrist]

All -

I learned something new today and thought I would share it with anyone
interested.

Apparently, the Thermo choke used on my Jag Mk IX (and some early BN7/BT7s)
is a gravity fed device and is very sensitive to the level of fuel in the
SU's Carburettor float chamber.  This means if the level of fuel in the
float chamber goes too high, it will leak through the Thermo Choke and back
into the Carb.  It's actually a bit of a long path for it to go from the
Float chamber, through the SU carb body, through the Thermo choke, and back
into the SU Venturi chamber - my mind didn't understand this was going
on..... For normal SUs, if the fuel level goes to high it just goes out the
overflow tube on top of your float chamber.

In the case of a thermo choke equipped carb, this will never happen, it will
overflow through the thermo choke into the carb's venturi chamber.

Needless to say, I had a devil of a time to figure this one out, and to make
matters worse I had a float chamber jet which passed the blowing test, but
in fact was leaking when fuel was put to it.  My leaky carb problem was
fixed by replacing the jet with a new Grose jet I happened to have in my
kit.

Cheers,

Alan

'52 A90
'53 BN1
'64 BJ8


On Wed, Feb 18, 2009 at 6:38 AM, Mirek Sharp <m.g.sharp at sympatico.ca> wrote:

> I concur,
>
> I have a thermo choke on my '60 and it had never leaked.
>
> Mirek