Join Date: Mar 2002
Location: Austin, TX, USA
Re: Gas delivery
For some unexplained reason, transparent filters often have air in them, so it isn't necessarily a problem so long as your keeping the float bowls full under all conditions.
I suppose it might have to do with the fuel being under pressure while the engine is running and the vapors remain condensed. But when the engine shuts down and the pressure declines in conjunction with a hot motor, the vapors form.
If you have a automotive vacuum gauge, chances are it doubles as a fuel pressure gauge (low pressure that is). You could rig up a T to the last leg of the fuel line and measure the pressure. It should not exceed 5psi. I'd expect the pressure to decline slowly once the engine is shut down. If the pressure doesn't hold, you can disconnect the fuel inlet to the carb and plug the line. Then fire it up breifly (it'll die fairly soon without a fuel source), and see if the pressure holds better. If so, then the needle and seat in the carb are probably not sealing well and may be causing a rich condition as a result.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI