Hey Folks

I'm preparing to sell the the old engine and all the stuff I'll have no further use after the Swap. (i have no room)

Victim is a F-Body 1991 Firebird 3.1L V6 (LH0)
The new engine (that's at least the paln) will be an 5.3L GEN IV AFM Flex Fuel all aluminum (LC9) with a returnless fuel system. I'll use an 1998+ Corvette Regulator/Filter installed under the left hand back seat (in place of the old filter).

Do i still need the Vapor Canister on a GEN IV SBC ?

 

The vapor canister vents the tank as the fuel level drops, and lets the tank breathe with temperature changes. It doesn't have anything to do with fuel return. So, yes, keep it.

 

Now i got. Vacum is (also?) vented, not (just?) heated Air/Fuel.

 

Right. The air coming out of the tank from heat expansion has to go through a charcoal bed to absorb the fuel vapors. The bed is "purged" by pulling air through the bed from the outside into the engine.

Similarly, when fuel level goes down and the tank needs air to replace it, it comes through the charcoal bed.