Hi Brent,
Others have explained the purpose of these "drains". In my nearly
singular opinion, "silly thing" is exactly that. I guess they are there
in case the float valves on poorly maintained SU carbs, along with a
dirty fuel system, happen to not shut off, & allow fuel to run into the
engine. If it really was so important, Healey would not have left the
drains off of the tri-carb engines.
True, at times, there may be a bit of unburned fuel that enters the
engine & can cause cylinder oil film to be partially washed off, which
supposedly can increase cylinder & ring wear. I don't personally think
that this is a great problem. I note, approvingly, that practically no
other cars are equipped with manifold drains. A few old tractors maybe,
but few modern engines. It has been observed that in a very few cases,
there is sufficient fuel leaked into the cylinder to cause hydraulic
lock of the engine. In even fewer cases this has resulted in a bent
connecting rod. Mainly on "fuel dragsters". Most starters don't have the
power to bend a rod when hydraulic lock happens. If lock ever did
happen, it could be easily cleared by removing the plugs & cranking.
In my experience, with properly maintained & set up fuel systems I have
never had a SU carb flood. I just solder the fitting closed, dispense
with the pipes, & treat it as normal engines are. I think that removing
the "manifold air leaks", although they are minimal, makes the carbs
easier to tune. There will also certainly be less air leak with the long,
small bore pipes added as they will add air flow resistance & reduce the
"leak". If concours correctness were a factor, I would still plug the
drains & add dummy drain pipes. I think it is a solution in search of a
problem. Others will emphatically disagree with my opinion.
Adding the drain pipes has been explained if you wish to leave the air
leaks installed. Take your choice.
Dave Russell
BN2
Brent Barnes wrote:
> Backed her (60 BT7 Mk I dual carb) out this morning to tinker under
> the hood and discovered a nipple on the bottom front of the intake
> manifold that seems to be dripping raw gasoline! Right onto the front
> of the exhaust manifold! Took a couple of pics that I can forward
> (1+ mb each) if that will help identify what this silly thing is and
> why it might be spitting. ANY help is appreciated!!!
>
> Brent Barnes 60 BT7 Mk I
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