> 1. Does changing the height of the float bowl assembly
> relative to the
> carb affect the level of petrol in the carb jet?
Yes it does, when the engine is not running. When the engine is running,
the jet is full to the top, regardless. The "depression" above the jet is
fairly constant (which is why this is called a 'constant depression'
carburetor design) and is several inches of water. Fuel is slightly lighter
than water, so it takes less than 1/4" of vacuum to lift it 1/4" through the
jet, a small fraction of the available vacuum. Therefore, fuel flow and
hence mixture is primarily controlled by the gap between the needle and the
jet, not the static level of fuel in the jet. And any small difference will
be compensated for when you set the mixture.
> 2. Assuming that the answer to the question above is "yes", should I
> adjust the float valve tang to compensate for the now-increased
> level of petrol
> in the float bowl?
I believe the answer is "No". You have now assembled your carbs with the
right parts, so you should adjust the fuel level "by the book". Presumably
before, you should have been compensating for having the wrong parts.
> 3. Is there a manual way to confirm the optimum setting of the float
> level, say, by inspecting the level of petrol in the carb jet?
Certainly can be done, and has been recommended.
> If so, what's
> the indicator of "optimum"?
Unfortunately, I don't recall the recommended measurement. The level has to
be slightly below the top of the jet (so fuel can't run out with the engine
not running, even parked on a hill), but I don't recall by how much. Might
have been 3/16", but I'm just not sure.
Randall
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