I see some small lines in each chamber of the carburetor apart from the main gas line…but none of the little ones are connected anywhere … can anyone help me …? these lines where they go … or so they must be … the gas does not overflow there …
They are overflow pipes , if the float needles get stuck , fuel will flow out of them , and dump it on the ground !
The lower ends are retained by a small oval clip at the oil filter housing.
wooa…gas on the ground !!! and there is no risk of a fire over there … so it comes? there is no container just in case …?
That’s the way things were in times past. Similar to engine breather pipes discharging direct to the road before they were connected to the intake system.
The amount of petrol likely to be discharged is small and you smell it very quickly and turn the engine off. These tubes are on the ‘cold’ side of the engine, i.e. not the exhaust side, so the risk of ignition must come from another source.
Just a detail to note. If fuel spills onto the starter, don’t activate it until it dries out. This happened to my brother on a much older car after a small leak from the carburettor when stationary. He didn’t realise it had spilled onto the starter. Upon switching the starter, the engine bay erupted in a small flame.
It’s just a safety device. It dumps the fuel that would otherwise spill all over the place to a safe area, towards the ground. Also far away and aft of the distributor. A catch can would be more dangerous unless it was sealed, and then how would you tell something was wrong?
You can smell it very quickly.
Modern fuel injection, if a hose ruptures, it sprays fuel everywhere under high pressure.
Ok…im sorry …just in case … I’m new to this … If iam driving and if there is a petrol overflow … the car turns off by itself … or does not have any device to turn it off …
If the fuel supply develops to an overflow condition from the float bowl, it means the fuel level in the carburettor throat is also the same extra-high level. What this would do is cause the engine to run roughly or not at all as it is then very much out of tune. For a single carburettor, it would probably stall and leave you stranded, but a twin carburettor might be able to splutter on, saved by the good carburettor.
There is no automatic means to shut down the engine for this situation. As long as the ignition is on, the pump keeps the fuel flowing and doesn’t care where it goes. Like many of the fault conditions applicable to old cars, the driver needs to be aware of any changes in sound, smell, feel, function, etc.
In saying all this, I have never experienced this type of flooding whilst driving, in over 50 years of driving, only when working on the car. The cause is usually the float being held down by an incorrect adjustment between the float arm and the needle valve and the needle valve becomes wedged in the open position. It typically occurs after the float bowl has been emptied during maintenance work and the pump is turned on to refill the float bowl. Therefore it would be rare for this to occur when driving. Personally, I would have no concerns about this design in our older cars, it is a matter of being aware of how it is intended to work, and shut the ignition off if it is misbehaving.
Don’t forget to have two extinguishers - one fitted in the cabin and one fitted in the boot. The reason being, that they are of small capacity and they run out quickly.
Ok…important information … excellent … I will take note of everything … once I install the new gas tank and the lines and other parts … I ll send you a txt to see how I am doing with this project … see it turn on
Thanks much… I appreciate all information…
In cars a little newer than yours such as my '74 XJ12 the vent tubes were routed to a carbon canister that collected the fumes and recycled them back to the air filter chamber before the carbs, to be sucked in with the regular air/fuel charge going in to the intake manifold. If you were concerned about air pollution you could rig up the same thing.
I extended my overflow pipes an extra foot towards the ground using rubber tubing that easily fit over the metal pipes, Any gas that might spill goes way out of the engine compartment. I have had fuel smells and diminished performance on a long hill. I’m sure the bowls were getting too much fuel.
I also have a fuel pump shut off switch which allows me to shut the pump off if I smell fuel and also about 45 seconds before I get home I will have depleted the fuel in the bowls and not get fuel boiling and hard restarting with bubbling fuel. I realize I may have to adjust the float level to avoid this problem. On long twisty roads I smell fuel as the bowls get tossed around and fuel goes into the overflow pipes. Something I live with. I DO have TWO fire extinguishers and they really don’t last that long!!
interesting … how do i get an off shift…how did you install it
do you mean the off switch? I have a toggle wired under my seat with wires going under the carpet into the trunk tapped into the fuel pump power switch. It also serves as a theft deterrent if someone were to try and drive away.
Just another tip, Gerard. From the conditions you describe, you seem to have frequent fuel smells. If everything is set up correctly, you should have none. If you are experiencing overflowing problems, it could be the shut-off valve in one fuel bowl not seating properly. This is a common cause of an annoying light overflow.
You can do a cursory check by carefully removing both fuel bowl caps after a run when you have had the problem. Firstly check the bottom of the overflow outlets while the engine is running and see if there is any fuel visible, and if so, you will know which is the offending carburettor. The caps are complete with the float and shut-off valve. If one bowl is overfilling, the free level of fuel will be higher in it.
Other causes of excess fuel supply are when the valve is shut late because the float level is set too high, or the float is not fuel-tight and is heavy.
One other cause of fuel smell I once had was more obscure. After some frustrating time going through the usual checks to no avail, I removed the carburettors and found that one jet was adjusted down to its maximum rich position. It could not return to its correct setting because it was seized in the jet seals. This was allowing more fuel through than could be burnt. This also explained why I could never quite get the tuning right. Just one of the many details expected from a 50 - 60 year old car.
I have grosse jets and neoprene floats so that takes two factors out of the equation. I think the float high needs to be checked and I will also check other components of the carbs.