[Healeys] overflowing fuel into intake drain tube

[WILLIAM B LAWRENCE]

Hank, the fuel level in the bowl is the same as the level at the bridge. If the fuel level is too high, or if the bowl is overflowing the fuel will also run out of the jet. I suspect the casting for the float bowl top, either a crack or a damaged thread in the needle valve orifice. Either will cause your symptoms.

Bill Lawrence
BN1 554
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From: WILLIAM B LAWRENCE <ynotink at msn.com>
Sent: Sunday, December 22, 2024 11:31 PM
To: Hank Leach <gradea1 at charter.net>; Hank Leach via Healeys <healeys at autox.team.net>
Subject: Re: Re: [Healeys] overflowing fuel into intake drain tube


Hank, I think replacing one component at a time might get you to a solution faster.

In a case not related I recently spent several days diagnosing a carburetor problem (surprisingly not SU) with no progress only to give up and check the distributor. My new condenser was bad out of the box. Someone said that 90 percent of carburetor problems are electrical. Case in point.

Bill Lawrence
BN1 554
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From: Hank Leach <gradea1 at charter.net>
Sent: Sunday, December 22, 2024 11:15 PM
To: WILLIAM B LAWRENCE <ynotink at msn.com>; Hank Leach via Healeys <healeys at autox.team.net>
Subject: RE: Re: [Healeys] overflowing fuel into intake drain tube

Bill-this car is 588 just 30+ from your car so about the same age parts-very old. I just mentioned that I'm swapping the floats and needle valves per carb for a test check. The float lids, although the shut off point for the incoming fuel, do not affect the fuel going out the bottom of the bowl to the carb body. I have a new NOS body and all new old stock gaskets, valves, etc.so I could "build" a new carburetor.

Being as anal as I am, I have put off that thought as I was trying to not use replacements but rather all original parts on my car. Yes, some small cracks in that old casting could be the cause. I may have to give in and replace the old duffer with the new item in the box. Hank
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From: "WILLIAM B LAWRENCE" <ynotink at msn.com>
To: "Hank Leach via Healeys" <healeys at autox.team.net>, <gradea1 at charter.net>
Sent: December 22, 2024 at 2:53 PM PST
Subject: Re: [Healeys] overflowing fuel into intake drain tube

Hank, Mike is correct that the jet needle is not intended to be a stopper for the jet. In fact in theory it shouldn’t even touch it. Considering that this appears to be a chronic problem on only one carburetor and with all you have attempted to correct it, it seems to me the problem is a defect in the carburetor itself. If the needle valve and float are in good condition and in adjustment the fuel level in the bowl and at the venturi bridge will never be high enough to run out of the jet. It seems that there is a flaw or a crack in or around the needle valve orifice that is allowing fuel to leak past the needle valve. Have you tried switching out the fuel bowl lid? Hope this helps. Good luck.

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: Sunday, December 22, 2024 8:28 PM
To: Healey team <healeys at autox.team.net>
Subject: [Healeys] overflowing fuel into intake drain tube

 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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