Weber Carbs Float Level Adjustment

Mike Flynn · 10-12-2018, 05:31 PM

Can someone give me more detail than is provided in the Porsche 911 Carb Rebuild article re the method of measuring the float level in weber carbs with the "paper towel method" after a rebuild? It has confused me, and I have both carbs ready to go back on the car - except for the float level adjustment. Surely there are some details missing in the article? I do not have a float gauge, so want to set them up using the method described, but cannot make sense of the article - slow learner, perhaps? When the paper towel is wedged between the float and the bowl I imagine it is elevated to its maximum height before measuring for the 18mm. But then later the article suggests the distance from the housing to the top of the float should be 12.5 - 13mm. Is this with the paper towel still inserted and elevating the float to its maximum height? Mine is nowhere near that - but perhaps I am measuring incorrectly? Appreciate any advice. Mike - Tasmania, Australia

1QuickS · 10-13-2018, 09:32 AM

Try looking at this procedure, it does require using float level vials:Performance Oriented

Norm01 · Norm01's Garage

Quote:

Originally Posted by Mike Flynn

Can someone give me more detail than is provided in the Porsche 911 Carb Rebuild article re the method of measuring the float level in weber carbs with the "paper towel method" after a rebuild? It has confused me, and I have both carbs ready to go back on the car - except for the float level adjustment. Surely there are some details missing in the article? I do not have a float gauge, so want to set them up using the method described, but cannot make sense of the article - slow learner, perhaps? When the paper towel is wedged between the float and the bowl I imagine it is elevated to its maximum height before measuring for the 18mm. But then later the article suggests the distance from the housing to the top of the float should be 12.5 - 13mm. Is this with the paper towel still inserted and elevating the float to its maximum height? Mine is nowhere near that - but perhaps I am measuring incorrectly? Appreciate any advice. Mike - Tasmania, Australia

This method requires the top plate of the carbs to be removed. You basically wedge the float at the furthest point from the pivot with something, usually a 1/4” rubber hose works well. You then set the top of the float (not solder joint) to 12.5mm above the carb plate, once set you measure and adjust the point where the needle valve touches near the pivot to 18mm from the plate. You still need to adjust the needle valve though, not sure it can be done well without the float gauge.

Mike Flynn · 10-13-2018, 05:14 PM

Thanks, I have read that excellent article, but as advised I do not have a float level gauge - yet! I read the tech forum before starting, and it seemed ok to try. It was necessary to rebuild the carbs as they were leaking fuel!!

However, when trying to do it as described after the rebuild, it does not give enough detail for me.

Am I the only one who has had this problem interpreting the details described?

I have found other tech articles very useful, but this one leaves me frustrated with a dismantled car on a beautiful day (for a drive!).

Any way, I have ordered the float level vial tool, (from Pelican) but it will not be in Tasmania for some time, so the drive will have to wait.

If anyone else can fill in the details that are missing from the tech forum, it would be greatly appreciated so I can get it back together at the earliest and fine tune it later when the tool arrives. Thanks again. Mike

Mike Flynn · 10-13-2018, 05:46 PM

Thank you s Norm. I just went down to the garage and retried. So, if I now have this correct, you adjust the paper towel or rubber hose packer wedging the float (and lower it from the 24.5mm+/- the full extent when the float is lifted to the max or the carb is inverted) down to 12.5mm to 13mm from the top of the float to the plate. You then measure the distance from the tag to the plate and adjust to get 18mm. Yes? Well, that's better!!! Makes some sense now!! I can then measure the 18mm from the plate to the needle valve. Thank you. Seems obvious now! Mike

911pcars · 10-16-2018, 10:59 AM

I may not have seen the doc mentioned, but here is the procedure using the Weber factory tools. Perhaps the author of that doc used another set of reference points. The factory uses the distance from the carb parting surface to the top of the float (12.5-13mm) (D) with their jig (C) in place. A curved length of spring steel (B) provides the tension to hold the float in that location. The PMO visual float gauge provides a dynamic measure of float/fuel level, but it helps to get it as close as possible if that area is worked on. There are only paper washers to add/subtract when using the PMO float gauge.

AFAIK, the float tools are NLA, thus alternate methods are employed.

Sherwood

1QuickS · 10-16-2018, 01:17 PM

The above procedure adjusts position of tab to be correctly in position with float when float is floating at theoretical position during running operation. This also assumes shim/gaskets and needle valve are all nominal to design dimensions.

It works well enough to assemble carbs for initial start-up after assembly. In fact, I have a dedicated float jig that I use in my work that allows me to perform the above static adjustments before they are installed into the carb body. I also adjust the tab to be perpendicular to the axis of the float needle valve which is important to prevent fuel leakage due to side-loading of the tip of the needle valve.

After all this I find that operational fuel levels are close to nominal but routinely need shimming to achieve specified fuel level in the bowl.