Classic cars forum & vehicle restoration.

[Rich5ltr]

I've kind of adopted my brother's Healey 3000 mkIII and today I took it for it's MOT and to have a few bit attended to. On getting it out of my mum's garage I noticed one of the float chambers was pissing fuel. Top off and a quick wiggle it was fine. The garage mentioned that it happened again whilst they had it and they gave the top of the chamber a tap. Spoke to my brother this evening who said it's happened before so... is this common? I've never come across it before and it's not like the car never gets used. I know I can easily replace the needle valves but I was just curious if anyone else had any experience of this.


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[Phil - Nottingham]

It can happen on SU's - sometimes its petrol gum caused by stale petrol after standing on the float chamber sides or pivot pin , it may be that the needle valve is worn
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[Rich5ltr]

Presumably just a case of cleaning them thoroughly?

[Phil - Nottingham]

Its well worth trying it - make sure parts are not lost and you may need new gasket for float chamber lid
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[Roger-hatchy]

If fuel is flooding the carb it will be a float chamber problem.

One way of checking the float level is to check the fuel level with the suction chamber and piston removed.

Fuel will not flood the carb with a bent needle, or for any other reason than an excess of fuel in the float chamber.

Clean out the float chambers, be carefull not to bend the forks, remove the forks, the pin comes out one direction only, if you have axcess to an airline blow through the needle jet, removing the needle first, saves hunting for it .

Only takes a small bit of dirt to obstruct the needle valve.

Not knowing what model SU you have, on some there is a small breather hole in the float chamber top, the air needs to go somewhere, make sure this is clear as well.
On the ones on my neighbours spitfire the bleed hole in just below the fuel 'in' pipe, might be covered by a tinplate moulding that is held on by the fuel pipe.
The previous owner had blocked on with a screw, and it was a while befor we realised why one carb kept flooding

Roger


PS edit
Just had a quick check
Your's will be HS4 carbs, there won't be any 'fork' in the float chamber, they have an integral float and arm, but the same goes the pin comes out one side only, this is obvious as one end is serated so as to be a interferance fit that way holding it in place.

[Roger-hatchy]

Just te-read your post and its the float chamber leaking?

Check the top, even with a magnifier, Mine had a hairline crack that would weep.

Try and see if the fuel is coming from the airbleed

Have you taken the filters off to check if the carbs are flooding when this happens.

One way to check the needle is to swap the 'in cap' parts, needle and float from one cap to the other, and see if the problem moves over.

This was when we found the airbleed on the spitfires carbs to be blocked off

There is not a lot that can go wrong with SU's,
The most crittical setting on them is the float / fuel level.

Roger

[Rich5ltr]

Hi Roger, thanks for your reply. The carbs are much bigger than HS4s indeed they are great big 2" HS8 buggers on the Healey!

When I said flooding I meant pissing out of the overflow pipe onto the drive, nothing as subtle as the carb flooding, this is full scale see how quickly the fuel pump can empty the petrol tank!

It's obviously a problem with the needle valve sticking in the open position despite the float floating at the top of the reservoir and it (obviously) being full of fuel).

I spent hours as a kid polishing and fettling SUs on our MGAs and Sprites (plus it seemed just about every car we ever bought) so I thought I knew them inside out but I've never come across this little (big) problem before...

I see that I can get needles from Burlen so that's probably the easiest answer. Especially as my Brother doesn't want to use it for a few weeks.

[oldtimer]

This is a well known problem and I would strongly recommend binning the needles and replacing with Grose Jets.These are far superior in my opinion.They are an American product but readily available here.I got them,one for each carb,from Moss,Darlington.
oldtimer

[Rich5ltr]

Thanks OT, I guess I've been out of the loop with regard to SUs for some years so I've not heard of those. I know Moss though so I'll give them a call and give them a try.

ETA - been researching Gross Jets (ball valves) on Google and it seems some people swear by them and others are less convinced. As SU (Burlen) still sell needle valves for the HS8 I might screw in a couple of those as replacements (they are only £6 each) and see what happens.

[oldtimer]

It is a quick and easy job to fit the Grose Jet assembly and I won't go back to needles.The original ones were brass and worked and wore in an acceptable manner.The modern needles are made of some plastic or composite material which I ,and others found less than satisfactory.The choice is,obviously,yours,but it is good that you know there is an alternative and one which I have found to be well made and wholly satisfactory.
Regards,
oldtimer

[mid]

my morris 10 used to do this when i first had it... trouble is it used to pour all over the exhaust manifold!

cleaned the fuel lines out and added an inline filter up near the carb, now its in regular use and the fuel tank is filled and emptied a lot more often it seems to have stopped doing this! touch wood!

it was amazing how much crap the filter took out in a very short period of time so guess it would have been quite easy to block things up

[Salopian]

I don't think its the problem here but I recall a friend a year or two back complaining he could not stop a carb on his MGTD flooding - he'd done the needle valve etc.
When I looked he'd missed the obvious (to me anyway to sound big headed) which was the half full float which had a leak on the seam. The float was just full enough to not quite rise sufficently to close the valve.
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Jonathan Butler
Alvis SD 12/50 1928 MG TD 1950

[lowdrag]

Already covered but usually the problem is stale petrol forming a laquer on the valve in the float chamber. A careful clean should sort it.

[Rich5ltr]

Thanks - to be honest I didn't expect to be baby-sitting a Healey 3000 but my brother has abandoned it and I feel sorry for it. So far I've bought a Accumate for it, put a cover over it, MOTd it, driven it... now I'm compiling a list of jobs that need doing; new wipers, clean/fix carbs, fix the rev counter, lubricate the heater controls (so I can turn the blooming heater off) replace the seat belt webbing, re-carpet it... the list goes on. I know what will happen he'll turn up in a few years time and say ah ha, my Healey, I'll have it back now it's driving well!

[Jim.Walker]

Float chamber needles sticking has been an SU problem for years. Quite often a sharp tap on the float chamber will stop it discharging petrol through the breather hole indefinitely. At other times, only changing the float needles will stop it.
The breather hole must NEVER be blocked off! Contrary to popular mis-conception, it is atmospheric pressure through that hole which PUSHES the petrol through the main jet. It is NOT "sucked" by the depression in the venturi. If that hole is completely blocked the engine will get no petrol at all! You cannot "suck" a drink through a straw! You suck and atmospheric pressure pushes the drink up the straw to fill your mouth!
I have just replaced the needle valves on my son's twin SUs because of flooding. Both original and new types are still available by mail order from the SU site on the web. They are not expensive.
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Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!