Carbs

[Barry20383]

I have bought 2 new needle valves and they have 2 x1mm washers with them will fit these and try the engine
Thanks.

[Barry20383]

Have recieved the carburetor gasket kits. In each kit there are 3 different size washers to fit under the needle valves how do i set the float level. Should i just keep the ones fitted to the recon carbs and accept they are correct. I have also bought new needle valves will this change the size of the washers.
Thanks for any info.

[Keith Clements]

I thought I had already explained that. Start 2mm but adjust if flooding or too weak on idle.

[David Morris]

Hi Barry,

As Keith says, start with the 2mm washers. If you can get her idling with dry carbs, that's half the battle. If she then 'picks up' smoothly from a blip on the throttle, you are home and dry(!), so I would leave well alone. If one or both are 'weeping' fit a second ( or thicker ) washer and cross your fingers.

Stay safe ,

All the best,

David

[Barry20383]

Have fitted the emulsion gaskets the right way round and fitted the new needle valves with the 2mm washers.
This has now solved the leakes on the carbs and the engine is starting on choke.
The problem now is if the choke is pushed in the engine starts to race and the passenger side carb has slight icing at the base. The air screws are 1-1\2 turns out.
Looking down the barrel both butterflies are closed and both stops off.
Any ideas thanks Barry.

[Keith Clements]

Have you disconnected the throttle linkage, balanced the throttle screws for even air volume, set the idle mixture screws?

[Barry20383]

Have set the carbs as you said but still not running well and backfired once.

[David Morris]

Hi Barry,

Some thing sounds wrong with the throttle linkage? Having set the carbs up as Keith suggests, my advice would be to reconnect the link rod between the two carbs and, with the choke fully out, look down the barrels and check that the throttle butterflies are both nearly closed and at least equal?

What worries me is that things seem to be happening in reverse when you push the choke in? When you pull the choke out, there is a connection on one of the carbs that increases the throttle opening, to make sure she doesn't stall. When you push the choke in, this temporary addition to the throttle should disappear and the tick over should slow down. Some people have a clothes peg on the choke pull rod, just behind the knob, to give an intermediate position. I know I do!

For some reason, you have the situation where this situation is reversed? I would have a close look at the mechanism fitted to the carbs. By the way, the icing is probably nothing to worry about. It is caused by the change in state from a liquid to a gas within the carbs, which naturally drops the temperature in the carbs. Normally, the heat from the heads melts the ice and if you have just the one carb showing ice, it just means that head is running colder.

Personally, once you have her ticking over, I would further tune the carbs by very gently increasing or decreasing the length of the connecting rod running between the two carbs. Take great care, as your hands are close to the fan! I use a synchronmeter to fine tune the length of the rod, to give an equal reading on the air inputs to the carbs. You might find them wildly out! On tick over, my engines runs at about 7 on the synchronmeter gauge. The balance is VERY sensitive to adjustments to the length of the rod. Just 1mm movement in the length of the rod will throw out the balance completely. Synchronmeters are widely available, at around £30. Try Amazon or eBay, if you don't have one?

All the best and Happy Christmas!

David

[Barry20383]

Already have the meter as i had a Bristol before the Jowett which had 3 carbs so this was handy.
Best to start from scratch tomorrow will pump fuel and fill the bowls and see if any fuel is coming out the emulsion block outlets to check the washer sizes.
I was wondering if the rod which opens the butterfly when the choke is put on is not letting the butterfly close when the choke is taken off would this cause the engine to speed up. I have the old carbs can check how much it should operate. Will check everything tomorrow and let you know how i get on.
Thanks for your help. Barry.

[Forumadmin]

My article on a Jowett patient may assist. You may be wrongly assuming the fault is with the carbs.
If you are certain the car was running reasonably with the old carbs then put them back , perhaps one by one, and see if the engine returns back as it was.
It is all too easy to change something such as timing, ignition leads, vacuum advance or spark plugs as well as the many things you know you have changed.
A backfire is more likely to be valve or ignition timing.

[Barry20383]

Am still having problems while turning the engine over on the starter petrol is leaking from the back of the bowls.
I fitted 2mm washers and new bowl gaskets. Is it possible if the level is too high in the bowls petrol can leak from the slow running jet pin holes where the cut out is in the emulsion block gasket. Any ideas thanks.

[Forumadmin]

You have 4 bowls and 4 floats. You should be able to eliminate the bowl and the float from the equation. Then you are left with the washers and the needle valve.
Take both bowls off very carefully without spilling any petrol and see where the level of the petrol is in each.
The petrol should only come out of the flute and not be leaking out. It is drawn out by the vacuum.

[Barry20383]

Have found why the carbs were overflowing. I changed the needle valves with new ones which were a different shape and were not seating properly and leaking from behind the washer. Have now put the old valves back which has stopped the leaks am trying different washers. Started as you said 2mm and 1.5 mm but engine still not drawing petrol i have 1mm yet to try. Thanks Barry

[Keith Clements]

By drawing petrol ..do you mean not starting?
Choke is required to start which creates a high vacuum and this weather probably needed till the engine warms up.

[Barry20383]

Not starting with choke. Have compression and spark.
Was running ok with choke until carb fuel leaks.