[Formulajones]

Exactly that's the whole point. You guys have something else going on. It's not the fuels fault. It doesn't just disappear in thin air unless you're excessively heating it or leaking or?????

A different issue needs to be addressed.

There is a reason why multiple cars of mine don't have the problems described here and I don't need a pusher pump

[Shiny]

My takeaway: If a carb goes dry in 2 or 3 hours, it's not typical, but by itself, I don't know that it matters if it starts and runs well when the bowl is filled again.

If it goes dry in 2 days, that's probably in the range of normal for a vented carb with an effective anti-drainback valve. Going dry in 5 days is well within the range of credible evaporation rates. Here's one example:

https://forums.maxperformanceinc.com...0&postcount=20

Way too many variables to guess at the underlying causes for the difference between 2 hrs and 2 days. Temperature and leaks are just two possibilities. Other factors include fuel formulation, vent size, bowl volume, and I'm sure there are more.

All these things are hard to measure and diagnose. For me, I think adding an electric pump fixes all of the possibilities if I decide I don't like cranking.

Mike

[Kenth]

Originally Posted by Formulajones

It's not the fuels fault. It doesn't just disappear in thin air unless you're excessively heating it or leaking or?????

You wouldn't think that the increased heat from the engine a while after the engine is turned off would cause the fuel to evaporate?

[HWYSTR455]

Yeah, heat is a big factor, and the amount of fuel too. A QJ bowl is fairly small.



.

[Formulajones]

Originally Posted by Kenth

You wouldn't think that the increased heat from the engine a while after the engine is turned off would cause the fuel to evaporate?

Yes but the problems start and worsen from these guys wanting to excessively heat these carbs in the first place, running the engines hotter than they really need to be and various other factors and then wonder why heat soak is so bad and why their fuel is boiling away. Instead they want to blame the fuel.

I'm running the same crap fuel, actually considered worse out west here than many other states, yet it's working fine for me on the Vega, the firebird, the Camaro and chevelle. I don't have extra pusher pumps on any of them. Bowls aren't drying up and even after sitting for 4-5 days and even a couple weeks in some cases I don't have to excessively crank the car to start it. The nomad will sit a month at a time and it still cranks and starts within 5-8 seconds and I don't even use the choke. I find that perfectly acceptable and no different than when these cars were new.

[Kenth]

Engines get hot from burning gasoline, there's no getting around it.
And heat is one of the three factors in converting the liquid fuel into a combustible gas. (the other two are velocity and amount of fuel).
The fact that the temperature of the engine rises slightly after the engine is turned off is nothing new.
The problem of fuel evaporation has always existed.
Luckily, the engineers who designed the Quadrajet didn't make the float housing any larger than necessary so that fuel loss could be kept as low as possible.
Then the fact that the oil pressure builds up during the time it takes for the fuel pump to fill the carburetor before the engine starts was certainly part of the design.
There are treatises written by smarter people on "The Principles of the Internal Combustion Engine" and "Car Engines and Motor Fuels" to read if you are really interested in the facts on the subject.

FWIW

[Formulajones]

There's engines get hot from combustion and then there are those that choose to make things hotter for no real reason. And when you do that you accelerate the issue.

Pick your poison.

But I think the point got across that fuel just doesn't disappear into thin air all by itself in a half hour that others state. It's accelerated by other means, and that can for sure be manipulated to ones benefit if you so choose.

[Shiny]

Originally Posted by Formulajones

......

I'm running the same crap fuel, actually considered worse out west here than many other states, yet it's working fine for me on the Vega, the firebird, the Camaro and chevelle. I don't have extra pusher pumps on any of them. Bowls aren't drying up and even after sitting for 4-5 days and even a couple weeks in some cases I don't have to excessively crank the car to start it. The nomad will sit a month at a time and it still cranks and starts within 5-8 seconds and I don't even use the choke. I find that perfectly acceptable and no different than when these cars were new.

What specific pumps do you use? Do you have a way to measure the drainback through the pump?

If you use aftermarket pumps, what style (2 line, 3 line, short, tall ??) and specific brand?

If you use a tall style pump that deadheads at 9 or 10 psi, do you have issues with flooding at idle?

I like the sound of your 4-5 seconds much better than my 15.

Question remains whether your crank time is short because you fill faster or lose gas slower?

Assuming your Nomad sits long enough to dry out from evaporation, the fact that it fills in 5 seconds tells me your pump is pushing a lot more fuel than mine.. either that or mine is draining all the way back to the tank, which I guess is possible ???