Quadrajet with no charcoal canister vent...

MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
113
Des Moines, Iowa
#1
what do I do when my carb doesn't have the big 3/8 nipple on the front? How did the earlier cars run the emissions hoses?
 
Canon_Mutant

Canon_Mutant

G-Body Guru
Aug 15, 2015
908
648
93
#2
This isn't me [hopefully Tyler won't mind] but he has the basic idea . . . should be useful. If I am misunderstanding your question, repost, I'll try to help or confuse you more (y).

 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
113
Des Moines, Iowa
#3
The carb I'm looking at for a replacement has no hole for the vent tube in the body. I wonder if the passage would still be in there so I could just drill and add the tube.
 
RegalBegal

RegalBegal

G-Body Guru
Jul 10, 2009
640
416
63
Lebanon, New Hampshire
#4
Just leave it open at the canister so the fuel tank can vent. The whole idea of that port is so as gas is pumped out of the tank it needs to draw in air, so by drawing it through the vent in the carb fuel vapors will be drawn back into the tank instead of gioing into the atmosphere. Earlier cars didn't have this, they just vented into the air.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
23,522
4,238
113
Kitchener, Ontario
#5
If you want to add the vent tube you need to take off the horn to make sure the port and channel are there in the older style carbs. The circled port in the body lines up with the channel in the horn for the bowl vent tube..

carb-1-jpg.92122
carb-2-jpg.92123
 
Last edited:
Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
5,515
909
113
Queens, NY
#6
How old is that carb? They used to have a vent on the top of the air horn with a spring loaded rubber disc. At rest it closed the hole and at any throttle opening it opened. The hole was closed up approaching emissions carbs but you still saw the castings for the spring and plug mechanism. I forget what year it happened but the vent tube was added to the carb, the tank had a non-vented gas cap, and the charcoal canister appeared.
 
Canon_Mutant

Canon_Mutant

G-Body Guru
Aug 15, 2015
908
648
93
#7
And you have to be a little careful on leaving open ports on that canister. It is amazing how much vapor that thing will absorb. When I moved it from PS to DS over my dual CAI mod, I thought I knocked or cracked something loose in the gas line. Started smelling gas. Nope, just that canister.
 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
113
Des Moines, Iowa
#8
Just leave it open at the canister so the fuel tank can vent. The whole idea of that port is so as gas is pumped out of the tank it needs to draw in air, so by drawing it through the vent in the carb fuel vapors will be drawn back into the tank instead of gioing into the atmosphere. Earlier cars didn't have this, they just vented into the air.
And the cars smelled like gas.
 
RegalBegal

RegalBegal

G-Body Guru
Jul 10, 2009
640
416
63
Lebanon, New Hampshire
#9
And the cars smelled like gas.
I would think you may have some other issue, maybe a bad line or the canister itself has a crack. The system should be drawing in air via the canister as fuel is used. I've done this to several cars over the years and never had that issue. On one car, i capped the canister and actually built up a vacuum in the tank to the point that when i went to gas up, the tank poped out with a loud noise. The other way you could go is to plug the canister and get a vented gas cap like older cars had or modify the one you have.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
23,522
4,238
113
Kitchener, Ontario
#10
And the cars smelled like gas.
I have used quadrajets with no bowl vent tube and they did not smell like gas. Even with the vent tube the bowl is still open to the atmosphere with this tube...

36001jet5-jpg.92348
 

Similar threads

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot Mike's Montes P-S-T Southside Machine Performance UMI Performance

contact [email protected] for info on becoming a sponsor