"Air Supplier Tube" Question

[texasz]

The "air supplier tube" is #13 in the attached diagram.  What purpose does it serve?  Where does it go (looks like towards the engine bay)?

 

[SteveJ]

I believe it goes to a hard line to the engine bay. If I'm correct, it's represented in this drawing by vapor vent line. This is from EC-15 in the 72 FSM.

[jfa.series1]

@SteveJ has it right. The hard line comes up on top of the left frame rail and connects via a rubber line to the flow guide valve. This valve is a small aluminum casting mounted under the ballast resistor. You can see the hard line and valve not yet connected in this pic. As to the purpose, the valve routes fuel tank vapors and oil pan vapors to the back of the air filter box so they can be pulled into the carbs and burned.

Edited August 3, 2021 by jfa.series1

[texasz]

@SteveJ and @jfa.series1 for the info, using what you both provided I found the line and am attaching pictures of where it goes under my hood.  Clearly there have been issues, you can see the dry/cracked hoses and electrical tape on one (assuming this is because it was cracked through), also the fact that one of the hoses is missing (I'm guessing this is the one that would go to the air cleaner housing).  Something that will be interesting is what to do with the hose that currently goes to the crank case breather because my new engine (an L28) does not have a provision for this, it only accommodates the one large hose.  Any thoughts on that?

 

 

 

 

 

[jfa.series1]

Great pics of what you found. I suspect the oil breather pipe from your L24 would fit the new L28 and allow you to retain the flow guide valve piping. If not, you could cap the one inlet nozzle on the flow guide valve to retain the one from the fuel tank. BTW - hold on to all those little OE spring clamps and refinish them in satin black for originality.

Edited August 3, 2021 by jfa.series1

[texasz]

21 minutes ago, jfa.series1 said:

BTW - hold on to all those little OE spring clamps and refinish them in satin black for originality.

Yes, I'll be holding on to and reusing those.  Satin black, thank you for that tid bit!

 

I replaced nearly all the fuel hoses in the rear of the car this past weekend and found several of the OE hose clamps missing and in their place the typical style you would buy at any auto parts store (worm screw style).  Time to keep an eye out for any OE ones I can get a hold of on the cheap to have refinished when I do a full restoration later down the road.

[texasz]

I have a few related questions...

What is the direction of flow towards the engine (the direction of the arrows in picture)?  

Is there a check valve in that block that only allows flow in the direction of the arrows (see picture)?

If both of the above are true would it be alright to have both hoses coming out of the that block go to the air cleaner?

 

Edited August 4, 2021 by texasz

[jfa.series1]

2 minutes ago, texasz said:

I have a few related questions...

What is the direction of flow towards the engine (the direction of the arrows in picture)?  

Is there a check valve in that block that only allows flow in the direction of the arrows (see picture)?

If both of the above are true would it be alright to have both hoses coming out of the that block go to the air cleaner?

 

There is a check valve in the body of the flow guide. The arrow on the bottom right should be reversed, flow is from the block to the valve. So... you have two inlets (tank and block) and one outlet to the air filter.

[texasz]

29 minutes ago, jfa.series1 said:

There is a check valve in the body of the flow guide. The arrow on the bottom right should be reversed, flow is from the block to the valve. So... you have two inlets (tank and block) and one outlet to the air filter.

Perfect although now I have another question...

The small hose coming from the block breather tube flows TO this check valve which the directs flow to the air cleaner.  The large hose that comes off of the block breather tube flows to the balance tube between the carbs (see pic for both).  This seems redundant to me.  What am I missing or not understanding?

 

 

For anyone wanting to use these pictures in the future I've corrected the flow arrows through the check valve (see pic below).

 

[jfa.series1]

Yep, seems redundant to me as well.  But... I 'm not a Nissan engineer in 1969 trying to get on top of emissions.

[DC871F]

FSM says the routing from air cleaner to flow guide valve does just that FROM air cleaner.

 

Routing is, FROM tank, FROM air cleaner, TO crank case.

 

The cleaner is vacuum. So FROM can't mean routing in the FSM surely, or does it? But do arrows lie?

[texasz]

18 hours ago, DC871F said:

FSM says the routing from air cleaner to flow guide valve does just that FROM air cleaner.

 

Routing is, FROM tank, FROM air cleaner, TO crank case.

 

The cleaner is vacuum. So FROM can't mean routing in the FSM surely, or does it? But do arrows lie?

GREAT CATCH!!  I would believe the FSM and the picture you show here is exactly what I was asking (which direction is the flow of each hose).  Thank you for the update on this topic.