Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: 1983zsled on April 14, 2016, 01:22:01 PM

Title: Blocking off front vent?
Post by: 1983zsled on April 14, 2016, 01:22:01 PM

I have just rebuilt a 1708 5586 carb for my .030 over 396 BBC for my 66 Chevelle SS. I have built a few carbs with Cliff's books, parts and guidance. Without getting to long winded, My 66 does not have any canister for the evap off the front of the Carb. OK to plug or no?
I have a mechanical fuel pump, stock lines from the gas tank etc.
I have searched the net and some say yes, others say no, that blocking it will cause issues.
As far as I have read and understand it's sole purpose is a vent, however there are other places the carb vents right?

Thanks.....

Title: Re: Blocking off front vent?
Post by: carmantx on April 14, 2016, 04:00:28 PM

Think you are fine to block off that vent tube.

Title: Re: Blocking off front vent?
Post by: 1983zsled on April 14, 2016, 07:39:03 PM

Ya I think so too. Whats the worst thing that can happen? I don't think that there is that much vent demand?

Title: Re: Blocking off front vent?
Post by: Cliff Ruggles on April 17, 2016, 01:51:47 AM

Only one vent is needed for the fuel bowl, but most q-jets will have several other places that the bowl will vent, and the POE wells may also have external vents on many models.  The POE vents can be internal, but you must have at least one external vent for the fuel bowl so it can fill when pressurized fuel passes the N/S assembly......Cliff

Title: Re: Blocking off front vent?
Post by: markedmondson on May 02, 2016, 07:12:46 PM

The canister has a vapor hose connected to the car's PCV system.  It also has a vacuum line connection to the front of the Q-Jet used as a signal, not a vent.  If your car does not have a canister, just run the PCV line normally from the carb (it's the port on the front of throttle body, below the fuel inlet) to the PCV valve, and plug the unused vacuum port on the carb.