Weber 40 IDF float level heights?

Timo · Post by **Timo** » Fri Sep 07, 2007 12:14 pm

OK I am currently rebuilding the Weber 40 IDF carbs on my 69 912 and I would like to check that both of my float level heights are correct. Does anybody know the correct height they should be?

fetuhoe · Post by **fetuhoe** » Sat Sep 08, 2007 11:15 am

With the carb cover held vertically and the float hanging from the fulcrum pin and the float level arm just touching the the needle ball (but not depressing the ball) the distance from the float to the car cover face, wiithout a gasket, should be 10mm. If not bend the tab retaining the needle hook.

Tilt the cover so that the float moves away from the cover and the tab makes contact with the needle valve seat. The fully open dimension of the needle valve should be 32.5mm, if not bend the tab that which contact the needle valve seat.

This means that the needle valve stroke should be 22.5mm.

Timo · Post by **Timo** » Sat Sep 08, 2007 12:17 pm

Weird, mine are at present near side carb = 11mm in closed position and 23mm in open position. Off side carb = 12mm in closed position and 25mm in open position. The weird thing is that the near side carb was stained with fuel on the outside of the carb body as if the float level had been too high and fuel had been overflowing so I've set both the closed positions to 12mm. If 12mm is too low what else could be causing fuel overflow? Also 32.5 seams a massive difference to my 23/25mm fully open, would this cause much detriment to the way the car ran? Surely my flat out fuel mix would be way out?

fetuhoe · Post by **fetuhoe** » Sat Sep 08, 2007 3:08 pm

I took these figures from a Weber IDF manual so they should be correct for the 40IDF.

If your carb has been flooding with the gap at 12mm then I would suspect that the needle valve is shot and has not been sealing and you are effectivel deliveirng fuel pump pressure to the float bowl.

The head of fuel above the main jet is the critical dimension and if you have 11mm on one carb and 12mm on the other then one carb will be slightyly richer than the other.

The drop distance is set by the stroke adjusting tab rather than the height adjusting tab and both need to be set correctly.

The opening stroke would only affect how quickly the reservoir can refill

Timo · Post by **Timo** » Sat Sep 08, 2007 3:32 pm

Cheers for the info, I've just been and checked my needle valves and they both look pretty shot tbh. I have changed them both and set the float levels to the weber guide settings so fingers crossed everything should be OK now.

Many thanks

Tim