70-72 vs 73 vs 74 Fuel Rails + Euro balance tube question

[Matthew Abate]

Okay, I have searched a ton of places and can't find the answer to this nor a diagram to help me from the FSM, Chilton, or Haynes manuals:

1. If I want to go with a euro balance tube on my SU setup, which rails can I make work?

2. What is the third tube for on the 73 and 74 fuel rails / pipes? Where does it go?

I had assumed I would need a 70-72 fuel rail / pipe to work on the euro balance tube, but I'm not certain. I have a three tube one that is either from a 73 or a 74 (not sure) and had assumed that third tube was part of the emissions system. I've seen people talk about cutting it off, but nothing clearing up what it is for.

I'd love some help (and directions to some comprehensive diagrams and illustrations).

[Captain Obvious]

That top tube is the purge line from the carbon canister system. I think the 73 still used the flow guide system and in 74 they updated to a full blown evaporative capture system. Meaning... I think that fuel rail is from a 74.

But the bottom line is... Unless you're running a charcoal canister evap system in the stock location, you can cut off that top tube with no problem.

[Matthew Abate]

So here's are two questions that spin out of that:

1. If one end goes to the charcoal canister, what does the other end of that third tube plug into?

2. If the charcoal canister helps with vapor lock and the gas smell, can this work with what I'm trying to do, or did I negate that by choosing the euro balance tube? I am assuming that it all plugs into the balance tube with this question because I can't find diagrams that I can decipher and I understand this mod less than I thought I did.

Edit: the charcoal system needs a '74 gas tank for the vapor line, doesn't it?

[Captain Obvious]

1) One end goes to the charcoal canister, and the other end attaches to the complicated 74 balance tube.

2) Charcoal can could help with gas smell, but won't do anything for vapor lock.

All years have gas tank venting one sort or another... The difference is what they did with the fumes. Prior to 74, they "stored" the gas fumes inside the engine block, and after 74, they routed them to be grabbed onto by activated charcoal in the carbon can. I'm not sure about the very early years (like 70), but prior to the carbon canister, they used a device called the "flow guide valve" which directed fumes into the non-running engine crankcase. In 74, they updated the system to the charcoal can.

Does that help? 

[Matthew Abate]

Yes, it does. Primarily because now I know there is no way to plug the rail into the balance tube, which is what I originally thought before I got confused.

Thanks.

One last question: is it possible to disassemble these in a way that I can save or replace the plastic bushings or are they pretty much fused together?


Sent from my iPhone using Classic Zcar Club mobile

[munters]

I took them off to powdercoat the rail.

[munters]

Double post.

 

Edited January 25, 2017 by munters