Holley carb leaks gas
I'll try to answer the why.
If its coming out from the tube connections:
When the engine is running the fuel in the lines leading to the bowls is under pressure.
When the engine is off, the lines remain at the running pressure but over time some fuel evaporates from the bowls and the inlet valve opens. That relieves the pressure.
Fuel inside the bowl is at atmospheric pressure. The only time you might see a leak that is squirting fuel from inside a carb is if the inlet valve is stuck open. When someone earlier mentioned float, that's what operates the inlet valve.
I'll try to answer the why.
If its coming out from the tube connections:
When the engine is running the fuel in the lines leading to the bowls is under pressure.
When the engine is off, the lines remain at the running pressure but over time some fuel evaporates from the bowls and the inlet valve opens. That relieves the pressure.
Fuel inside the bowl is at atmospheric pressure. The only time you might see a leak that is squirting fuel from inside a carb is if the inlet valve is stuck open. When someone earlier mentioned float, that's what operates the inlet valve.
