setting the float level on my IDA's....puzzled

[frank912]

Hi All,

I am just working on my weber IDA and tried to set the float level. In the past I have done this according to the book....so float out 12.5-13mm en then the tab at 18mm.

I recently acquired a P77 measurement tool and I would like to know what the correct fuel level would be when the bull is full. Have been searching for an hour but the only thing I can find is when the fuel should stop entering the bull. so, when the fuel bulb is full and if I remove the top of the carb:

What would the distance be from the 'top' of the carb (where the gasket lies) to the fuel?

18mm from the top, or 12,5-13?

Thanks a lot, frank

[1QuickS]

Design specification is top of float is 12.5 to 13.0mm from top of main body without gasket.

Fuel level in the float bowl when all assembled is 20.75mm plus/minus 1mm from top of main body without gasket.

Tab on float is 18.0mm plus/minus 0.1mm from top of main body without gasket.

All three dimensions are when fuel pressure is 2.5Meters of water or 3.56 psi. Difficult to measure when disassembled. This is why I like the external fuel level gauge. Engine runs to stabilized fuel level (& fuel pressure); shut off engine & check fuel level using gauge.

I offer detailed fuel level setting procedure here: http://www.performanceoriented.com/s...-procedures-1/

If you try to measure to the fuel level after removing the top of the carb then the float will rise and the fuel level will drop.

I have measured several fuel floats in their "running" position after blueprinting them to OEM design. The result is that float tops vary plus/minus 1mm in height around a nominal 13mm height when fuel levels have been adjusted to the same height using the external vial.

Mechanically setting float levels introduces several measurements which are prone to an accumulation of measurement errors in addition to geometry errors in the float geometry. The external vial is a direct reading of actual fuel level in the bowl... a much more reliable & accurate method.

[frank912]

Hi Paul,

Thanks a lot for your reply!

The 20,75mm is the number I was looking for. As long as this number is correct (measured using a P77 tool, correctly calibrated) then the other numbers are not relevant (the 12,5-13 and 18mm)? These numbers are the numbers that should lead to the 20,75 mm result, right?

Thanks, frank

[1QuickS]

When all is right with the float geometry, fuel pressure and float needle adjustment then the fuel level will be 20.75mm below top of main body which is the Weber specification. The P77 tool has lines scribed that correspond to this specification and the other numbers are not relevant, at least not super relevant. They are important in that the tab on the float needs to be perpendicular to the axis of the needle valve when the fuel level is 20.75mm down. If the tab is not perpendicular (at least fairly close to that) the resulting slope of the tab will generate a side load on the tip of the fuel needle which can upset the sealing efficiency of the needle with its seat. The potential result is a seeping of fuel when it should be shut off or worse, sticking open. Another issue to be aware of is the divot in the tab from wear with the end of the needle, this divot needs to be peened flush with the surrounding surface so the tip of the needle won't stick open; peen from the back side of the tab.

So, the 13mm & 18mm numbers are important to check float geometry to avoid issues as mentioned. I made a jig to check/adjust float geometry & I find about 5% of the floats I check (over 1200 floats so far) have OEM geometry, some are close & others are surprisingly out of whack. Since the main circuits are activated when air flow through the carburetor is sufficient to suck fuel from the float bowls it should be apparent that float levels set using standard gaskets as opposed to shimming will result in main circuit activation at different times during acceleration. About 9 out of 10 projects come to me with a gasket under the needle valve as opposed to being shimmed.

[frank912]

Hi Paul,

Thanks for the help. I have set the levels correctly now and this takes aways a lot of the nasty fuel smell that I was experiencing. My float level was around 13mm below top of bowl. Not sure whether this makes sense.

I do have another problem: because of running the car now with the correct fuel level my car runs less rich. I am experiencing a major problem until 3.000 rpm.

I have a 2.2S engine, weber ida3c's, 130 main, 55 idle, F3's and 32 venturi's. I am also not getting a decent response from my mixture screws. The engine is new/rebuild and was running great.

My first thought was to up the mains, but this did not make a difference. Went back to the 130's, then tried 60 idles...... no change. To be honest.....my mixture response has always been weak but the car was running perfect with the high float level, only starting it with a hot engine was a problem (probably because of fuel leaking on the plugs).

Any suggestions on what I could try next?

The car is now impossible to drive, especially with a cold engine. Does not climb easily in rpm till 3.000 (without a load), nearly stall when you use throttle at idle..... I am again puzzled.

Regards, frank

[edmayo]

Check your ignition timing, doesn't sound like it's advancing correctly.

[1QuickS]

Follow Ed's advice, jetting sounds right. You will need to verify air flow balance at idle & @ 3000 RPM and adjust for Lean Best once ignition timing has been verified. One thing to check is the rotor moves freely (remove distributor cap and check the rotor rotates freely & returns reliably) and then check advance using timing light.

[frank912]

Ok, I will do that as soon as I find the time for this. I did go back to the F26 emulsion tubes yesterday and this improved the performance below the 3000 rpm a lot. Nonetheless I will make sure that the advance curve of my distributor is like it should be and check the timing.

General question: if backfiring through the exhaust occurs and there is no air leak...... could ignition timing cause this? If so.... is this in general a sign of to much advance or too little?
My guess would be that there is too little advance or timing set too late , but just checking


Thanks a lot.

Regards, frank

[1QuickS]

If no air leaks in exhaust system or gaskets from headers to muffler then retarded timing and rich mixture can cause a backfire.

If decelerating with closed throttle then lean mixture can ignite rich mixture gasses in muffler, assuming you were rich at time of closing throttles.

Cracked distributor cap and other ignition issues can also cause this.

My best offerings subject to better responses.