What exactly is the purpose of the 'tank purge' line in the engine compartment? Does some type of vapor come out of that line? Does a vaccume need to be present for the function of that line? Or is is some type of pressure release thing.. When I removed the rats nest I just capped it off.

Also the line on the oil filler neck, i've seen a 'vented catch' can hooked up to it on other peoples cars here, and others just put a breather on it, but didn't it have a vaccume present when the rats nest was present? I just capped that off as well.

Any clarity on these 2 lines and their functions would be appreciated. I read info on another post but they didnt go into much detail about them.

 

Run the tank purge line to your charcoal canister so the fuel tank can vent and not become pressurized. Either put a breather filter, or run a line to the breather box off the oil filler nipple to vent the crankcase. If not, you'll get condensation in the filler neck.

 

Your crankcase needs mild vacuum from the carb mainbody (manifold vacuum is too much) to suck out the water vapor that enter the crank through blow-by.
It seems as though boosted applications can get away without it. I don't know this for a fact, nor do I know why (seems counter-intuitive to me).

The fuel tank needs to be able to breath in order to supply the carb. When the tank warms up, fuel vapors will expand and contract on their own, so you don't need the PCV hooked up to the fuel canister.

The two were seperate systems merged for convenience to allow for complete close-off of the whole system when the car is shut down (via the float bowl vent solenoid valve) for emissions purposes.

 

The tank purge line keeps the tank in an air-starved condition to insure that the tank doesn't blow up when the wiper on the sending unit inside the tank arcs.

Also, when the motor is shut down the tank purge line vents fuel fumes into the carbon canister, where they are absorbed until the motor is restarted and the carbon canister itself is purged by vacuum.