Non EEC fuel tank vent

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ASPEC

ASPEC

Junior Member
Joined
Oct 29, 2024
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Location
SURPRISE, AZ
First Name
-
Truck Year
1974
Truck Model
C2500
Engine Size
454
Hello,
Does anyone have a pic or diagram of the fuel tank vent hose/breather for a 1974 non eec 454?
The PO had capped both tank's fuel sender vents and that is a big no-no. To make matters worse they installed the wrong filler necks (79-84 instead of 73-74) and the caps are not vented either.
I checked the service manuals but didn't find anything. I am assuming it is similar to a differential vent but would like to know how they were run and if there is anything special about the vent type.
Thanks in advance. :)
 
75gmck25

75gmck25

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Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
My ‘75 has three port sending units, and both sides go to a T fitting. That fitting connects to a metal line that runs up to the engine compartment.
At the engine compartment it connects to the vapor canister, and that originally vented into a dedicated port on the carburetor.

In the engine compartment I now have just a vent line from the canister to an open fitting I put on the base of the air cleaner, since my newer Quadrajet does not have the right ports for the canister vent. It probably doesn’t pull much vacuum, but seems to be enough to clear the canister of any vapor.
 
ASPEC

ASPEC

Junior Member
Joined
Oct 29, 2024
Posts
6
Reaction score
21
Location
SURPRISE, AZ
First Name
-
Truck Year
1974
Truck Model
C2500
Engine Size
454
75gmck25 said:
My ‘75 has three port sending units, and both sides go to a T fitting. That fitting connects to a metal line that runs up to the engine compartment.
At the engine compartment it connects to the vapor canister, and that originally vented into a dedicated port on the carburetor.

In the engine compartment I now have just a vent line from the canister to an open fitting I put on the base of the air cleaner, since my newer Quadrajet does not have the right ports for the canister vent. It probably doesn’t pull much vacuum, but seems to be enough to clear the canister of any vapor.
Click to expand...

I appreciate the response but this '74 2500 came from the factory with NO emissions systems. No evap, No cats, No air pump, etc...
So it won't be the same as any model with an evap cannister.
 
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