Fuel Return Line Question
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Fuel Return Line Question
I haven’t run an “active” return line since I had a Quadra-Jet on my motor way back in the day on the 350. The return line is still there but it goes to nothing. I want to get rid of it all together but have a couple of questions. I currently have the fuel tank down and the return line disconnected. Basically what I was going to do was take a rubber vacuum cap-off boot, put it on the 5/16” return line barb that is coming out of the fuel tank and clamp it on there. Is this ok to do, or is there a more proper way to go about this that I am not aware of? My other question is by capping this off could I possibly create a problem with the fuel flow to the carburetor (by air locking it or what not)?
The problem I used to have with the return line in place is that when I would fill the tank above ¾ full it would start siphoning out of the return line until it reached ¾ tank then it would stop. I want to be able to fill my tank up full again (considering the long journey to GA that I have ahead of me).
The problem I used to have with the return line in place is that when I would fill the tank above ¾ full it would start siphoning out of the return line until it reached ¾ tank then it would stop. I want to be able to fill my tank up full again (considering the long journey to GA that I have ahead of me).
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
When I still had my original gas tank - I just put a piece of fuel line on the barb on the tank and closed it off with a screw in it, tied down with a clamp... However - my '68 gas tank cap is vented unlike the gas cap on your '74.. Therefore - I don't know if it's safe to do that on a '74.. However- you could also go with a vented '68 style cap..
BTW - I got a new gas tank that doesn't have the barb .. so I didn't need to plug it...
BTW - I got a new gas tank that doesn't have the barb .. so I didn't need to plug it...
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Several ways to plug tank return line.
I think ur idea using that vac cap with a clamp sounds fine. 
But maybe fill that cap with JB Weld before install. Or even just plug line with JB Weld overnight and go. Just don't use any silicone sealer- no silicone sealer. Simplest method would be to stuff a bolt with threads cut-off (just shank remains - no threads) into rubber fuel line and clamp at both tank line and bolt ends.
BTW the fuel tank on a '74 (like mine) vents through the Emmissions Vapor Canister (EVC) through smaller lines that run down the drivers side and finally into carb by ported vacuum. NAPA still sells the EVC (charcoal canister) if interested (part#CRB 229817 or maybe it's 2-29817).
Good luck #13.
cardo0 
But maybe fill that cap with JB Weld before install. Or even just plug line with JB Weld overnight and go. Just don't use any silicone sealer- no silicone sealer. Simplest method would be to stuff a bolt with threads cut-off (just shank remains - no threads) into rubber fuel line and clamp at both tank line and bolt ends.BTW the fuel tank on a '74 (like mine) vents through the Emmissions Vapor Canister (EVC) through smaller lines that run down the drivers side and finally into carb by ported vacuum. NAPA still sells the EVC (charcoal canister) if interested (part#CRB 229817 or maybe it's 2-29817).
Good luck #13.
cardo0
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Thanks for the tips guys. I ended up just using a vacuum cap and clamped it down with a fuel line clamp. I put the fuel tank back in just a few moments ago. One less project to worry about. Thanks again.
Team Owner
Joined: Aug 2000
Posts: 21,457
Likes: 463
From: Massillon,Ohio USA
2020 C3 of the Year Finalist - Unmodified
Cruise-In VI Veteran
St. Jude Donor '08-'09-'10-'11-'12
1975-'82 type caps are really a cap within a cap. All you need to do to make this a vented cap is simply drill a small hole on the inside(inner)cap. My '75 has been "vented" this way since '94 when I took my tank's bladder out, but that's another story
