BJ8 Carb overflowing

[shorn]

Drove my 64 BJ8 today and noticed a strong fuel smell. Popped the bonnet and noticed fuel literally pouring out of the overflow tube on the rear float chamber. These are HD8 SU's. Does that usually mean that I have a sticky needle and seat (jet) assy. or does it mean a float that doesn't anymore? I am not experienced with SU's other than some simple adjustments. So what do I look for first?

 

[Keoke]

Drove my 64 BJ8 today and noticed a strong fuel smell. Popped the bonnet and noticed fuel literally pouring out of the overflow tube on the rear float chamber. These are HD8 SU's.
Does that usually mean that I have a sticky needle and seat (jet) assy.

Yes due to dirt or wear.

For this Case tapping on the fuel bow, with the handle of a plastic screw driver may temporarily correct the problem

or does it mean a float that doesn't anymore?

If it is a float that does not float any
more it is easily seen resting on the bottom of the float bowl after the float bowl top is removed.

Replacement with new is the best solution here as well as the case of a worn needle valve. I like Crose Jets


I am not experienced with SU's other than some simple adjustments. So what do I look for first?

---Keoke

 

[Michael Oritt]

It's not too hard to isolate the problem.

First pull the lid off the float bowl and see if the float is sunk--if so replace.

If the float is okay your problem might be a sticking needle--if so replace.

Failing that check the float level by letting the fuel pump run, then shutting off the ignition and removing the top of the carb and the piston to check the fuel level--you should see fuel just below the top of the jet. Adjust the level by bending the forked arm accordingly--more space between the arm and the needle lowers fuel level and vica versa. If you have the newer plastic floats then bend the attaching arm.

 

[shorn]

Thanks, it was the float. Although not totally full of fuel, there was a significant amount in it when shaken. I could see two small cracks on the side of the float. Replaced the bad float. I also adjusted the hinged levers as both appeared to rest low on both carbs. I used a 7/16 drill bit to measure. The Healey starts, idles better and runs well. Will probably get better mileage too.
The only question I still have is, "why would you place the overflow tubes in such a way that the fuel could end up spilling onto the front exhaust pipes?" I guess a fire would let one know the carb is overflowing!!!!!

 

[healeynut]

All -

Fuel overflow is usually caused by 1 of three problems:

1) Sunk Float - Note that both Keoke and Michael (although very very smart car people) don't have this exactly correct. Sunk floats will usually still float. The only way to really confirm if your float is bad or not is to remove it from the float chamber and shake it - if you hear fluid sloshing around inside the float, your float is bad & must be replaced.

2) Crap in your fuel - this is probably the most common problem, exacerbated if your are using Grose jets. Grose jets are VERY sensitive to rust and scale in the fuel, original SU float jets less so (but still a problem). If you don't have a fuel filter somewhere before the float chamber, you should put one on.

3) A bad float jet - sometimes the little rubber tips simply wear out. This can actually be pretty hard to detect (don't ask how I know this!), really the best way to check is to replace the jet with one that you know works (e.g. swap the jets from front to back and see if the problem reverses, or simply use a new or good used one if you have it in your kit).

:thumbsup:

 

[healeynut]

"why would you place the overflow tubes in such a way that the fuel could end up spilling onto the front exhaust pipes?" I guess a fire would let one know the carb is overflowing!!!!!

Shorn - this is because your BJ8 is missing the hoses which go from the ends of the overflow tubes and snake through the hole in the front bottom of your heat shield and end somewhere around the bottom of your chassis - you won't have a fire if set up properly like from the factory.

 

[shorn]

Well, I have no hoses from the banjo/vent pipes on my car. I guess I haven't noticed them on other BJ8's either. I do notice the hole in the front of the heat shield. So do hoses from both vent pipes go through the one hole? Or do they tee together first? It does make a lot more sense to dump the fuel somewhere other than on the exhaust system. Thanks

 

[AUSMHLY]

Well, I guess I haven't noticed them on other BJ8's either. I do notice the hole in the front of the heat shield. So do hoses from both vent pipes go through the one hole? Or do they tee together first? It does make a lot more sense to dump the fuel somewhere other than on the exhaust system. Thanks

Hi Shorn,

You may not have noticed them on other BJ8's because you were not aware of it. Or, they were missing theirs too. Image that!

You can buy the rubber hoses at the local auto store. Make sure to tell them they are fuel hoses.

Two lines go through the one hole.
I also used a rubber grommet in the hole.

Drive it like you stole it.
Roger

 

[germanmichel]

Hello,

some days before I think also about the overflow tubes.
On my BT7 the two overflow metal tubes outer diameter approx. 2mm come out of the inlet manifold. (If I remember near 1. and 6. zylinder) They run very near to the exhaust manifold (1mm). This is really a funny feature, also the carburettor mount directly on the exhaust manifold....
After I stop the engine, out of the tubes comes two or three bubbles petrol.... Has someone a picture for the original and correct forming of the pipes ?
Why it is not possible to close the holes in the manifold with a plug ? Is there a risk for boiling the petrol in the manifold with a result of starting problems ?

Bye michel- who did not like this technical solution really...

 

[Michael Oritt]

Sunk Float - Note that both Keoke and Michael (although very very smart car people) don't have this exactly correct. Sunk floats will usually still float.

Alan is <span style="font-style: italic">partially</span> correct--

The general definition of the verb "To sink" is: "To descend to the bottom; to submerge". "Sunk" is the past participle form of "To sink" as in my statement: "...see if the float is sunk...." I should have said "...see if the float is <span style="font-style: italic">partially or entirely </span>sunk...." I'm glad we cleared that up!

Now here's a brilliant idea to which I am hereby relinquishing all rights and putting out into the public domain in order that some enterprising person can make his fortune: Make carb floats out of self-skinning gasoline-impervious, non-absorbative closed-cell foam. There, I've said it, it's out there, and I can't take it back. How long till we see these in the Moss catalogue?

 

[Keoke]

Michael did not like the technical solution presented because he thought they were talking about the Manifold drain tubes. The tubes in this discussion are long rubber tubes fitted to fittings on top of the HD8 carbies which handle carb overflow problems exclusively. Contrastingly. the metal tubes you are referring to are fitted to the intake manifold and are used to minimise engine flooding on start up. No you should not plug them up!---Keoke

 

[germanmichel]

Hello all,
thank you Keoke for your answer. I know I was a little bit off topic, but I think my question was near the topic. All this drainage solutions are risk for life...because they drop all near the exhaust system...

Bye Michel-who would like to optimize this design solutions to reduce or eliminate this risks

 

[Keoke]

Hello all,
thank you Keoke for your answer. I know I was a little bit off topic, but I think my question was near the topic. All this drainage solutions are risk for life...because they drop all near the exhaust system...

Bye Michel-who would like to optimize this design solutions---

OK Keep them in good condition and properly routed to reduce or eliminate the risks to life.--Bye--Keoke