[Healeys] overflowing fuel into intake drain tube

[Michael Salter]

Very frustrating indeed.
I would comment that I don't believe that the needle is really meant to be
a "shut off" valve as there is always a tiny annular gap between it and the
jet. I presume that with the suction chamber and piston removed the fuel
level is observed to be at least 1/8" below the top of the jet.
I  can assure you that when everything is correct they don't leak.

M

On Sun., Dec. 22, 2024, 4:11 p.m. Hank Leach via Healeys, <
healeys at autox.team.net> wrote:

>  I have chased the cause of too much fuel exiting from the rear carburetor
> overflow of my 100 for years. These are H4 carbs-very simple design, but
> must be done correctly to perform. So I find that the jet is out of center
> and piston is sticking up above the flat about 1/8"-that would allow fuel
> to run into throttle area and out overflow drain tube.
>
> No way to center jet on car. Remove carburetor-a 4 hour job- and clean and
> replace gaskets and gland washers-yes cork- and reassemble and center
> jet...now works perfect. Re mount carburetor and connect fuel lines-another
> 4 hour job.  Both carb pistons drop with a clunk at the same time.  Turn on
> key- fuel pump clicking-overflow again leaking.
>
> I have reset the floats and float needles (brass) were replaced many
> times-that's not the issue. No fuel in float bodies-they are not leaking.
> I just cant believe its too much fuel pressure but then again, this is a
> British Car.
> Float is brass but when shaked it is dry. I filled the float lid with carb
> cleaner while holding needle valve closed and no leaking. That's two places
> checked (these are unfortunately "new" parts) Now the next leak could be
> between the needle and jet if not closed off-also new parts-jet .090.
> Needles are QW as specified but i also have a set of ATs which are lean
> that I am tempted to try. Actually both needles are about the same at top
> .089, but ATs are a bit fatter at mid range. Problem is all testing stinks
> up the garage and creates an explosive atmosphere so best done outside in
> the rain.
>
> I know some folks like Grosse Jets-but I don't-- I prefer the simple brass
> ones with viton tips which do work if pressure is applied by forked
> leg-also new, and set to 7/16" or MORE. With covers off, both bowls are
> equally about 1/2 filled. Fuel pressure is a thought as it can push by the
> stops but its the correct pump and when key on clicks fast then slows to a
> stop... but then tick, tick which it should not do!  Fuel is going out and
> down the drain tube to my swimming pool drip pan. Im tempted to measure the
> top of the needles to see if they are really at .089. Can't measure the new
> jet but its stamped "9" Maybe stick in a number drill to see if its round?
> Mind you, these carbs have about 125 miles total on them. As far as I know
> these are "genuine SU" parts-not Moss India knockoffs.
>
> I really thought that the centering was the issue and took the carb off
> for that reason which cured the drop-each drops equally with thud. That's
> not the problem. Any suggestions? Someone says use plastic floats...Hank
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