Carbs

[Barry20383]

Have fitted my re con carbs from JCS the problem is that when i started the car on full choke a lot of petrol is coming out flooding the spark plug holes.
On checking it seems to be coming from under the bowl near to the throttle butterfly spindle is this a common leaking area. I assume all new gaskets have been fitted.
Could this leak be from the emulsion block gasket and how can it be remedied Thanks for any help Barry

[Forumadmin]

It is probably the float chamber needle valve is not closing, possibly because your petrol pump pressure is too high or float not working.
There is lots on JT about checking fuel pressure.

Please reply to the topic rather than creating a new post.

[Barry20383]

The carbs i took off didn't have this problem so i assume the pump pressure is ok will check it anyway.

[Forumadmin]

The needle valves are sensitive. If you still have the original carbs take off the two bolts holding the float bowl. There should be an aluminium washer/spacer above the needle valve which acts as a float level adjustment. See if the same thickness is on the rebuilt carbs. Or just swap the needle valve and washer. Also blow them out as sometimes muck gets in there. Shake the float to make sure there is no hole in it letting in fuel. Make sure the float does float and does not get stuck on side of chamber. Check the needle valve closes by putting finger lightly on it when pumping petrol. Take care of course!

Replace chamber and float and manually prime pump. The fuel pump should stop pumping when the needle valves close.

[Barry20383]

Have taken both float chambers off and replaced the needle valve seating washers from the old carbs which were thicker. I have tested the valves by pumping petrol and holding the valve closed with my finger on releasing petrol is flowing. Have changed one float from the re con with one from the old carbs as the top of the float had a dent in it making the contact area with the valve at a slight angle. Have assembled the carbs the drivers side seems to have stopped. The passenger side is still leaking badly. It seems to be coming from under the back of the float chamber. Have looked down the bore and the accelerator butterfly seems dry.
Could this leak be from the emulsion block gasket .
Will have to look with a mirror.
Thanks Barry.

[Keith Clements]

So swap the float chamber body which has the emulsion block.

[Barry20383]

Will try swapping over the bowls the problem is i will be mixing parts from the old carbs to the recon carbs. I am not sure it is the gasket as its not weeping as you would expect its pouring out.

[Forumadmin]

Perhaps swap the needle valve first. It is more likely to be that.
You could (may be able to) also see if the recon carbs have new needle valves.
If you prove it is the needle valve then get back to JCS.
Their suppliers may have provided a bad valve or their reconditioner may not have changed them.
It is a common problem with classic car restoration that parts and procedures do not produce an 'as new' experience!
Unfortunately few are prepared to pay for an exhaustive examination of the part before recon, lots of time and expensive machinery to test and do the recon, and quality control afterwards. JCS is staffed by unpaid members who volunteer their time and skills to helping club members. They rely on like minded enthusiasts to help. The classic car industry is bugged by a few suppliers, who may be trying their best, but do not produce parts of good enough quality. There are many stories of faulty components being supplied from otherwise reputable suppliers. The source is often from Far East copies.
That said most things can be fixed. If you have a needle valve which works, even though it is old, use it. It has bedded in!

[Barry20383]

As you suggested i took each bowl off and held the needle valves up one by one with my finger and pumped no fuel came out only when i let go did fuel come out which shows no blockage . I put the thicker washers under the valves which seems to have stopped the leak on the drivers side which was only a small leak. The leak on the passenger side is a full leak emptying the carb in seconds. I can try first fitting a bowl from the old carbs that would prove the emulsion block gasket. The needle valves and jets didn't look new but seem to be working ok. While the fuel was leaking i looked down the barrel of the carb and the accelerator butterfly was dry is this any clue. Thanks Barry.

[Forumadmin]

I would hope that swapping the bowl which has the emulsion block will prove where the problem is.
Make sure you use a known good float though.

On the problem bowl take out the float. Fill with petrol up to the level of the fuel outlet that protrudes into the carb throat.
There should be no leak in the bowl body until you reach that level.
Drop the float back in which will displace some fuel but the leak should stop. The float should of course float.
You could do that on the known good bowl and see if there is any difference in float height.

There are only four components here, the valve, the washer, the float and the bowl, so you need to eliminate which one (or ones) are faulty.

From experience you can alarmingly find that when you fix one side the other side starts leaking. This is because the petrol pressure has transferred to the other side!
Some needle valves, if they have been sitting around, have oxidised so lapping in with Brasso helps.

[Barry20383]

Have put the floats in a bowl of petrol for half hour they are floating ok and no petrol inside. Will check the things you have suggested and re post.
Thanks for your help. Barry.

[Forumadmin]

Note it is not just that they float but they have the same bouyancy. If one is heavier because of resoldering it will float lower.

[Barry20383]

I filled the carb bowl with float as you suggested and petrol was pouring from the bottom of the emulsion block. I have taken off the emulsion block and found the gasket is on upside down. The gasket has a small square cut out which is at the top next to the jet. With the gasket upside down the gasket hole is over the emulsion block web allowing fuel to come out. I can't re fit the gasket as it has been punctured by one of the screws. Will have to check the other carb to see if its the same. Will now have to order new emulsion and bowl gaskets as soon as possible. Thanks Barry.

[Barry20383]

Will soon receive the new gaskets for the emulsion blocks to assemble the carbs. The problem now is which spacer to fit under the needle valves the original carbs had thicker washers than the re con carbs. Is there a level mark inside the bowl as i can pump fuel into the bowl until it stops then remove it and check the level then fit washers to adjust the level. Am fitting new needle valves to be sure. Thanks Barry.

[Forumadmin]

https://jowett.net/forum/download/file. ... &mode=view
C1316 requires 2 x 1mm washers or a 1mm washer and a deflector.
The fuel level will depend on many things such as the fuel density and temperature, petrol pump blow off pressure, float weight and valve competance.
So the only real test is to try it with a running engine in the car on a level surface. I do not think the level is that critical as the suction through the emulsion block has to accomodate the variations due to cornering, braking, acceleration and fuel delivery capability.
This is why fuel injection is now used!