[Healeys] overflowing fuel into intake drain tube

Mon Dec 23 17:58:08 MST 2024

My BN1 #724, engine number 139756, has no float bowl drain tubes, just the
red notched washer and chrome vent at the top screw .  I have never had the
problems that you report.  The floats are original.  I cleaned and rebuilt
with a Moss kit.  If one of my carbs worked right and one did not, after
replacing all rebuild able parts, I would replace the malfunctioning carb.
If that fixes things you can explore the faulty carb at leisure.  If it
doesn't, then the rear carb wasn't the problem.
-Roland

On Mon, Dec 23, 2024, 1:19 PM Hank Leach via Healeys <healeys at autox.team.net>
wrote:

> Michael-that is why I asked the question in the beginning, Where is the
> fuel coming from and what is the cure for the problem? I agree that the
> fuel is "atomized" in the throttle area and that would be the best
> condition to send it to the engine but this car is dumping fuel and I
> cannot find the mechanism to stop that flow. Suggested lighter nitrile
> floats are at the top of the list, if in fact my brass ones are bum. Bill
> Lawrence modified his intakes possibly due to fuel issues?  The system on
> this early car (same as yours) is a bit "cruder" than the revised float
> bowl vent system (with no manifold drain?). And, I cannot see anything
> wrong the float setting as presently set.
> The fuel is not coming out the jet with the key off and the float bowls
> full to proper level-it is as you said below the top of the jet. Float
> valves are closed.  Its when the key is on and fuel pressure is applied
> that I am getting the overflow condition. I was hoping that someone else on
> the team has had a similar experience. Hank
> --------------------
>
> From: "Michael Salter" <michaelsalter at gmail.com>
> To: "Hank Leach" <gradea1 at charter.net>
> Cc: "Healey team" <healeys at autox.team.net>
> Sent: December 23, 2024 at 12:21 PM PST
> Subject: Re: [Healeys] overflowing fuel into intake drain tube
> Sorry Hank but I think you have that wrong.
> In and SU carb,and for that matter almost every other type of carburettor,
> fuel DOES NOT pump out through the jet.
> The fuel level, as mentioned previously, is controlled by the float
> chamber float valve to never actually be above the top of the jet. It is
> only the flow of air across the carburettor "bridge", where the jet is
> positioned, that draws fuel up through the jet to be atomized into the
> airflow and into the inlet manifold.
> This is all related to Bernoulli's principle
> <https://www.google.com/search?client=firefox-b-d&q=Bernoulli%27s+principle>
> which is the basis upon which all carburettors work.
> If fuel is coming out of the jet when the engine is not running then the
> mechanism controlling the float level is not operating correctly.
>
> M
>
> On Mon, Dec 23, 2024 at 1:37 PM Hank Leach via Healeys <
> healeys at autox.team.net> wrote:
>
>> Ah! A rebel in the crowd. I looked at a bunch of photos of 1953 100
>> engines on the web.  Many are configured as mine with NO FLOAT BOWL DRAIN
>> TUBES.  The *later *engine setups have drain tubes in the lid. This
>> includes the cars using H6 carbs (Lemans).  Also, on these early designs
>> there is a different carb adaptor. Part 1B1672  which has a lower drain in
>> the casing up to engine # 139915 (my engine 139563). Of course Moss,
>> etc. only sell the later style products. but some books show the solid
>> float lids and some show vented lids and some show a lid with a drain tube
>> (air vent).
>>
>> So, in theory the way the early system works; fuel is inlet from the
>> float chamber and enters the jet thru a hole in the tube positioned between
>> the two gland washers which are to keep the fuel intact. when the choke is
>> pulled that jet hole  is lowered to send in, as the British say..."a neat
>> petrol supply" to start the car.
>> Now, if you turn on the key, fuel pumps in and is moved thru the jet into
>> the throttle area and into the manifold. Unless the engine is now turning
>> and suction from the piston is active, the fuel will run haplessly in the
>> intake manifold and out the drain tube to the ground. So the important
>> procedure in these early systems is turn the key and crank the engine
>> immediately or it will overflow fuel down the drain tube.  I'm here
>> testing the operation of the carburetors in a static mode-its not going to
>> do anything but spew fuel to the ground. Right?
>>
>> The later design using a float bowl vent tube also send fuel into the
>> manifold but without a drain tube the fuel will go into the engine, as the
>> Moss PDF described, diluting the oil and washing the cylinders. Sounds like
>> the best method of starting up is to crank the engine as soon as you hear
>> the fuel pump click...I typically have waited until the pump stopped (float
>> bowls full) before cranking. Live and learn?Hank
>>
>>
>> --------------------
>>
>> From: "WILLIAM B LAWRENCE" <ynotink at msn.com>
>> To: "Hank Leach via Healeys" <healeys at autox.team.net>, "Bob Haskell" <
>> rchaskell at earthlink.net>, "richard mayor" <boyracer466 at gmail.com>, <
>> gradea1 at charter.net>
>> Sent: December 22, 2024 at 9:29 PM PST
>> Subject: Re: [Healeys] overflowing fuel into intake drain tube
>>
>> I’d like to be able to answer that, but I have to confess I’ve modified
>> the induction system on mine (I know, I’m going to Hell) and I’m a little
>> fuzzy on the details. If memory serves (a doubtful premise) the float bowls
>> originally had an open vent arrangement on the top with no drain tubes. The
>> car was built up from several dozen boxes of parts, so that may not have
>> been correct. About 20 years ago I built a pair of H6s and installed those
>> with drain tubes. The car is a bitsa anyway so originality is secondary, or
>> maybe tertiary…
>>
>> Bill Lawrence
>> BN1 554
>> ------------------------------
>> *From:* Healeys <healeys-bounces at autox.team.net> on behalf of Hank Leach
>> via Healeys <healeys at autox.team.net>
>> *Sent:* Monday, December 23, 2024 1:59 AM
>> *To:* Bob Haskell <rchaskell at earthlink.net>; richard mayor <
>> boyracer466 at gmail.com>
>> *Cc:* healeys <healeys at autox.team.net>
>> *Subject:* Re: [Healeys] overflowing fuel into intake drain tube
>>
>> Thanks Bob-yes the Moss site confirms they have alternate nitrile floats
>> and about $20 each. Looking at the diagram there is a drawing of the float
>> chamber overflow AUC1866 (451-250) $24.99 each.  I do not have these
>> overflows on my float bowls (as Richard Mayor mentioned their location)
>> Instead the early cars have silver vent caps and a red washer which allows
>> air out and those two intake manifold copper drain pipes at the bottom of
>> the carb intakes. There is a PDF note on that part which reads:
>>
>> "These pipes are open to the atmosphere, for two reasons: first (and most
>> important) they allow the fuel coming into the float bowl to displace the
>> air in there so the fuel can reach its correct level in a timely manner.
>> Second, if the float valve (needle-and-seat) should stick open (as they do
>> when a bit of grit is trapped on the mating surfaces) the fuel will be
>> piped out and down – away from the engine. If the *fuel could not escape
>> through the overflow pipe, it would pour down the carburetor throat into
>> the engine*. With that much liquid gasoline, not all of it will vaporize
>> before the spark plug fires. The fuel that does vaporize will make the
>> mixture so rich (as if the choke were engaged) the car will belch black
>> smoke out the tailpipe. The engine will eventually flood and die."
>>
>> The point here is that not having those overflows on the float bowls; the
>> overflow is actually after the throttle plates on my car. I wonder how Bill
>> Lawrence's early car is configured and if he has float bowl overflows or
>> intake overflows? Is it possible that this is a clue to my delima? Trapped
>> air? Hank
>> --------------------
>>
>> From: "Bob Haskell" <rchaskell at earthlink.net>
>> To: <gradea1 at charter.net>, "richard mayor" <boyracer466 at gmail.com>
>> Cc: "healeys" <healeys at autox.team.net>
>> Sent: December 22, 2024 at 4:28 PM PST
>> Subject: Re: [Healeys] overflowing fuel into intake drain tube
>>
>> Hank,
>>
>> I think the newest floats are made from nitrile rubber - nitrophyl, not
>> plastic.  Supposedly unsinkable.
>>
>> Cheers,
>>
>> Bob Haskell
>> Austin-Healey 3000 roadster registrar
>>
>> On 12/22/24 17:49, Hank Leach via Healeys wrote:
>>
>> I actually cannot figure where all the fuel is coming from. In static
>> mode-key off and float bowls at proper level-with dashpot and piston
>> removed, no fuel is apparent (as Michael says about 1/8" below jet or as
>> you say equal to float setting). However, with key on and carbs together
>> it's a different story-fuel is flowing steadily. The suggestion that was
>> made that we really need to have clear plastic float bowls has merit. I
>> cannot tell if the brass float is pushing hard enough to shut off the peg
>> on the valve. When held shut by hand its positive.
>>
>> If the float is "heavy", then it will not effect enough pressure on the
>> peg to stop the flow. This is why someone suggested plastic floats instead
>> of brass. Fuel is the shut off mechanism. I have swapped float and needle
>> valves from front to rear carb in hopes that the front one will now start
>> leaking. That may be a clue to the issue. Waiting for a dry day (next
>> year?) to test that theory.
>> --------------------
>>
>> From: "richard mayor" <boyracer466 at gmail.com> <boyracer466 at gmail.com>
>> To: "Leach Hank" <gradea1 at charter.net> <gradea1 at charter.net>
>> Cc: "healeys" <healeys at autox.team.net> <healeys at autox.team.net>
>> Sent: December 22, 2024 at 2:23 PM PST
>> Subject: Re: [Healeys] overflowing fuel into intake drain tube
>> Hank,
>>
>> If I read your post correctly, the fuel is coming out of the jet in the
>> carburetor into the intake manifold and then out the drain tube.  Not from
>> the overflow tube on the float chamber. I’ll proceed with this assumption.
>>
>> The level of fuel at the jet is the same level as that in the float
>> chamber. That is the way these SU carbs are designed. That is why float
>> level is so important.  If fuel is flowing out of  the jet before the
>> needle valve shuts off the fuel supply at the float chamber then your float
>> level is set too high.  You need to close the float needle valve with the
>> float at a lower level. Instead of using 7/16th as a guide, try 1/2” and
>> see if that stops the flow.  But then you said you tried different
>> settings.
>>
>> Is there an obstruction that is preventing the float from rising all the
>> way to the top to close the needle valve?  Try a different float. Polish
>> the post.  Is there any wear in the fork or pivot in the casting that is
>> not allowing the needle to move feely into it’s seat.  I think that’s where
>> the problem is.
>>
>> Richard Mayor
>> boyracer466 at gmail.com
>>
>>
>> On Dec 22, 2024, at 12:28 PM, Hank Leach via Healeys
>> <healeys at autox.team.net> <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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