Hello,
I have a 86 iroc z with 650cfm holley carb. With the engine on, the primary float fuel level is correct. When I turn off the engine the primary float level decreases quite a bit. I live well down in Texas and is pretty. UHC very hot year round, and of course the engine is always super hot.

I read that the check valve on the fuel pump might be bad or evaporation of the gasoline. Either way, how would you set the level of the fuel?

Can this lead to any issue while driving?

thanks in advanced.

 

How long before the fuel level drops? Once the fuel is in the bowl it can't go anywhere with the engine off unless it leaks out or evaporates. Street car I'd set the float level with the engine running. I'd pull the bowls and check the condition of the floats, If in doubt put new floats in.

 

Does your Holley have fuel bowls with built-in sight glasses or sight plugs?

If removable sight plugs adjust the fuel level until it just barely drips out over the the threads at the bottom. If built-in sight glasses adjust the fuel level until it is in the middle of the sight glass.

Do you cylinder heads have exhaust gas crossover ports? Does your intake manifold have an exhaust gas crossover? If YES to both questions do you have the exhaust gas crossover blocked off?

Does your engine have a carburetor heat shield between the intake manifold and the carburetor?

Is your intake manifold spread bore or square flange? Is you carburetor spread bore or square flange?

 

Good morning,
hank you for both replies. The float is new. If I take the car for a ride in the morning, by the afternoon the gasoline is gone. I have not check in a pattern such as every hour or every couple hour to see if sooner. But where I live my garage is about 110 degrees and outside are about a 100 for most of the fall, spring and summer. The engine stay extremely hot for hours after turning off.

My car has side plugs. When the engine is running, the level is just right under the hole.

I don't know what a crossover is ...sorry, but if helps I have a 350 crate with Holley carb and long headers...nothing fancy after that.

Carb does not have a heat shield and intake and carb are square flange.

Hope this additional information helps. thanks.

 

Crossover is the passage in the intake from the heads that allows exhaust gas to pass through the intake to warm the choke and the manifold.
Even if the gas was evaporating if there is any in the bowl there will be gas in the accelerator pump well, if you pump the gas does the squirter squirt gas? There should be enough gas to start the engine and the fuel pump will fill the bowl quickly.
Now if you want to check your fuel pump the correct way use a vacum gauge on the intake port of the mechanical fuel pump. That will tell you is the pump can pull fuel or if the check valve is bad.

 

yes fuel evaps
phoenix resident
you can cure this by adding something that helps with the heat under the carb
a phenolic spacer, a heat shield, and yes in hot days the fuel can evaporate in the lines and causing Vapor Lock.
The cure is what all engineers did to nearly everything on the road today, electric fuel pump.

 

Spacer sounds is the way to go.

Beeman- yes the accelerator pump still squirting gas. The engine is turning on.

Not sure if this will cause issues with the engine or driveability of the car.

 

Sounds like a non-issue, to me. If the fuel is "Gone"...i.e. not in view in the float bowl window...but the accel pump still works and the car still starts, what's the problem? On my boat, which has a Holley carb, when it sits for a long time (months) the fuel will evaporate out of the float bowl, and it is GONE....as in the bowl is dry as a bone inside. It takes a lot of cranking (probably 15 seconds), to get fuel up to the bowl, then fill the bowl enough that the accel pump will work, then the engine will start. THAT is a carb where "the fuel is gone".

If your car starts after sitting all day that is IMO, "Worryin' about chit that ain't worth worryin' about".