Float chamber float level

RobHomewood
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Float chamber float level

Post by RobHomewood » Wed Aug 24, 2016 5:42 pm

Does anyone know the correct level for the float for a Solex 30FFIA which I cannot find anywhere? As I understand it this is usually measured from the top of the chamber body including the gasket to the top of the float.
And should I use fibre or copper washers on the needle valve to adjust the height?

lakesrally

Re: Float chamber float level

Post by lakesrally » Wed Aug 24, 2016 8:03 pm

Not sure about on a 16 but on my P3 I had flooding problems when I first put the car on the road. It had a copper washer behind the needle valve, I initially cured it by putting a second copper washer in there. Eventually I discovered that the gasket was too thick, I fitted the correct gasket and removed the extra copper washer, been alright for many years ever since. I cannot give you a measurement though Rob, I'm away from home at the moment.

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luli
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Re: Float chamber float level

Post by luli » Thu Aug 25, 2016 9:22 pm

Basically the answer is yes, you can adjust the fuel level by this method. Remember though that the level is a balance between the float weight and the fuel pressure. If the fuel pressure is too high (incorrect pump) or the float weight is too high - the result will be flooding. nominal values are 1.5 Atm. and 26 grams. Are the surfaces really flat? It is easy to distort the carburetor body which is made of mazak by over tightening. You can get gaskets and repair kits from here: http://classiccarbs.com.au/index.php?ro ... y&path=482. See a little more here: http://wp.me/pXLKy-29V
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RobHomewood
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Re: Float chamber float level

Post by RobHomewood » Thu Aug 25, 2016 11:49 pm

Thanks Luli and Lakes Rally but unless I am to guess at the correct level by trial and error- there must be a measurement available somewhere as I have seen for other Solex's. I might guess that the 30FFIA would be the same as the 30FIA as that is the twin choke version for the 4 cylinder model but cannot get a level measurement for that either.
Can anyone come up with one please given that my fuel should eb between 1.5 and 2 and the float is marked 21.5 gp?

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47p2
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Re: Float chamber float level

Post by 47p2 » Fri Aug 26, 2016 6:14 am

The most likely cause of a flooding float chamber is a sticking needle valve. Mike Couldry sells replacement valves.
As far as I can remember it is soft aluminium washers that are fitted between the top cover and the needle valve

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luli
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Re: Float chamber float level

Post by luli » Fri Aug 26, 2016 8:51 am

Inspect carefully "Fig 27" in the above link. You can see that oo (the spraying orifices) and g (pilot jet) are on the same level. The fuel level must be a little above this level (otherwise the engine would not be able to idle) and below u (pilot air bleed) otherwise the fuel will overflow and flood the carburetor. Remember also that the fuel level relative to these critical points is changing with the car inclination so that it is not a fixed value. When the car is horizontal it should be in the middle between these two extremes.
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RobHomewood
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Re: Float chamber float level

Post by RobHomewood » Fri Aug 26, 2016 9:53 pm

Thanks for that Luli.
When you say 'below' item 'u' pilot air bleed do you mean the top of the screw head or the bottom of the tip?
I shall blow that drawing up to scale (by checking actual dims I can measure) and measure off the different heights for the range you suggest. This at least will give me a chance of getting it somewhere near right.
Rob

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luli
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Re: Float chamber float level

Post by luli » Sat Aug 27, 2016 6:35 am

Below means that fuel would not be able to flow into it and block the air bleed.
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RobHomewood
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Re: Float chamber float level

Post by RobHomewood » Sun Aug 28, 2016 10:00 am

Thanks Luli but I am somewhat thrown by this illustration from the Arnolt Corps Solex manual for a generic float chamber [img][IMG]http://i172.photobucket.com/albums/w27/RobHomewood/Rover%20P2/Solex-Carb-booklet%20Fig%206%20Page%2011_zpshxru4dz3.jpg[/img][/img] which clearly shows the fuel level well below the spray orifices in the choke tube and if you look closely on your illustration there is faint hatching representing fuel shown at a similar level. Or have I misundertood? Any corroborative info one way of the other would be much appreciated
regards Rob

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luli
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Re: Float chamber float level

Post by luli » Sun Aug 28, 2016 11:30 am

I have made some measurements on a 30FIA carburetor – they are easy to make and you can repeat and verify them on your 30FFIA. When the float chamber is totally empty, and the float sits on its bottom, its top (where the needle valve is actuated) is 14 mm below the top flange level. The needle valve can reach as low as 11 mm below that flange. Its full travel, when completely blocking the fuel flow, is 2 mm. That sets the average fuel level at 10 mm below the flange. The spray orifices are 14 mm below the flange level.
However, all manuals state that the float/needle-valve combination depends also on the fuel gravity, which might have been changed over the (many) years since the car was designed.
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