[Healeys] overflowing fuel into intake drain tube
Bob Haskell
rchaskell at earthlink.net
Sun Dec 22 17:28:41 MST 2024
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>
> To: "Leach Hank" <gradea1 at charter.net>
> Cc: "healeys" <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> 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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