Carb Float Height, for Beginners

[BEEK]

if the float is too high it floods the carb, internally, fuel can run out thru the vapor lines and overflow into the venturi area. if it is too low you will simply run out of fuel causing a starvation situation. the float adjustment is not 100% critical, for 100% accuracy but it is real easy to get it correct. according to fiat the float level is supposed to be 6.5mm +/- 1mm so you have room to play

[JerryH]

Also, if too much fuel in bowl, increases issues with hot-soak starting issues.

I'm interested in learning about 'hot soak'. I've got a 76 1800 with dual IDF 40s. When the engine is cold, I turn the key to on, wait a few seconds with the electric fuel pump running, pump the pedal twice, turn the key, and she starts right up--very satisfying. When the engine is hot, I do the same steps, pump the pedal twice and she cranks for about 4 seconds before the engine kicks in. I suspect I'm experiencing 'hot soak', but I don't know what it is or how to correct it. Majic, would you mind explaining this?

[majicwrench]

It's just the fuel vapors filling in the intake and air cleaner. THen when you go to start is too rich and generally has to crank a few to purge some of that richness.
Really no "fix" it is just life with a carb, or two of them. A four second crank isn't that bad. If it takes longer than that, or blows black smoke on start up, or blubbers for the first 10 seconds, then something is amiss, like floats being too high. Fuel pump pressure too high can also make issue worse.
I would, however, try NOT pumping throttle when engine hot, it likely does not need that extra shot of fuel. Engine is already slightly flooded, hold throttle down half way.

My 72, when cold or cool, fires up so fast it surprises me. Then the right combo of hot day, hot engine, a 10? minute soak, and you have to crank for 3-8 seconds to clear. Such is life.

[JerryH]

Good explanation, thanks majic. I'll try not pumping the peddle when it's hot.

[131]

Good explanation, thanks majic. I'll try not pumping the peddle when it's hot.

I've got IDFs on my 2 litre, I have to start it on the accelerator pump when it's cold, it starts pretty quickly, but if I'm not pumping the throttle while turning the key there's no chance it will go. It starts first go when it's hot, holding the throttle just off idle as I turn the key.

[opus10583]

Hi,

Finally re-found it: http://www.redlineweber.com/html/Tech/3 ... akdown.htm

At the bottom there; what's accomplished by limiting the max drop to 43mm from 46.5mm?

Then from increasing it to 50mm?

And why?

Thanks!

Mark