Steve Tritle wrote:
>
> Gang,
>
> My TD has rebuilt carbs that I can not set to allow the car to idle
> below 1000 RPMs. The front carb has a weeping of gas from the bottom
> cork gland. Could that be the culprit? What to do?
>
> Steve Tritle
Obviously the carbs have not been rebuilt properly, or they would not be
leaking. When installing new cork seals it is useful to soak them in
light oil say 3 in 1, for a couple of days, prior to installation. This
will provide a swollen and a lubricated surface for the jet to slide on
and give a good leak proof seal.
It is vital to ensure the brass butterfly is correctly installed in it's
shaft, with the chamfered edges tightly fitting the interior bore of the
carb's body when in the fully closed position. This is best achieved by
lightly setting the retaining screws first, and then operating the shaft
by hand while watching light shining through the choke tube. When the
throttle plates have settled into their 'natural position' and the least
amount of light is visible, then tighten the screws, and set them. It
is also vital that the cross shafts are correctly fitting the carb's
body. Loose shafts will ruin any attempt for a reliable idle; tight
shafts in a rebushed body will expand with heat and can cause the
throttle to stick in the wide open position, resulting in embarrassing
situations not conducive to longevity. Assuming that all these points
are in order, it is now vital that the fuel level in the float chamber
is correct, and that there is no leakage of fuel past the inlet valve.
(I recommend the fitting of the Gross type of fuel inlet valves.). Any
maintenance manual will give you the relative procedures for this. I
need not reiterate here this readily available information.
After all these items have been attended to, arm yourself with a carb
synchroniser such as is sold by Moss. The oldies used to check for
correct balance between the two carbs by listening, via a short piece of
rubber tubing to the hiss, made when the engine was running, of the air
passing through the carbs' throat. Not very accurate, especially for
the hearing impaired person. The synchroniser will enable you to set
both carbs. independently of each other to the same rate of
inhallation. Again, clear instructions are included with the machine.
Follow the procedures laid down for mixture adjustment, and make sure
the dash pots are topped up with an oil to SAE 20 spec. It is VITAL
that the needle bearing piston be free to move over it's whole travel,
and that the needle is corrctly centered in the jet's orifice.
All throttle linkages must be free and lubricated in order that the
butterflies can close properly. The return springs should be in good
order, and the shaft interconnectors tightened cautiously to prevent an
undue differential twisting of one shaft in relation to the other from
spoiling the idle. I also recommend the fitting of a heat shield
between the carbs and the manifold. This will help prevent overheating
of the float chambers (which contributes to give an erratic idle) and
also vapourisation of the petrol, so common a fault when making short
duration stops on very hot days.
The S.U. Carburettor rebuilding video available from Moss Motors gives a
very clear explanation of how to do these jobs correctly. I am able to
supply you with a heat shield should you so desire.
Geoff Love, The English Connection.
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