After successfully installing that AB Valve from @zKars I just noticed I have 2 bolts plugging openings on my balance tube.  Seemed strange to me and was thinking the PO removed some emissions equipment but all the pics I'm seeing and FSM show the tube without these openings.  Did the PO grab a later year one?  Or maybe this car had some accessory like AC?  I did see in the original console the typical holes where ac controls would go but thought maybe he just parted out a console.  Any thoughts?  Any reason to bother replacing that tube?

Well, “Velly Intellesting”….

The back of the two plugs is usually a 71-72 location for the vacuum fitting out to the brake booster. Only the early balance tubes had that fitting going out the end horizontally like yours. 

What I see is a bit strange. The hose fitting in the back of your balance tube with the hose that I assume goes to your brake booster, looks suspiciously like a PCV valve….. Can you take the hose off and show a pic with the whole hose going over to the booster?  

You have the PCV in the regular place in the center of the balance tube where it belongs.

I cannot figure out what the other plug is meant for quickly. Couldn’t see any picture on Google with it used. Your balance tube is NOT the later 73-74 style for sure

Edited August 3, 2024Aug 3 by zKars

Weird right, couldn't find a single pic anywhere on any site of that setup.  I must have the unicorn lol.  That hose does go to the booster, I just replaced it when i refreshed all the old crap hoses.  i specifically bought the early series 1 since i had the horizontal fitting.  the setup has the typical valve mid hose in the support bracket.  that fitting on the tube is just a plane fitting no valve like the type coming off the coolant lines to the carb coollant tube.

By 12/70 Datsun had swapped the location of the vacuum hose to the most right top hole in the balance tube and plugged the horizontal hole. One less bend in the hose. It does look like the fitting for the hose did not change and just looks like PCV, but it's not.

Mystery solved. So for me I guess  the previous owner just happened to have a series one hose use that and when I inherited the car I copied his selection. Sounds like no harm no foul correct? You would think if they preferred moving it to the vertical position why wouldn't they have just made a tube with only one location? Why manufacture a tube with two additional holes that you have to stick bolts in?

Probably some possible future use or different market scenario. Who knows what the intent of the plugged hole just to the left of my vacuum hole is for. Like the wiring harness including the hookups for electric fuel pump which made it easy for me to convert to electric fuel pump on my 12/70 car.

9 hours ago, w3wilkes said:

Probably some possible future use or different market scenario.

Maybe your market is the "different market" concerned...?

 

 

Even the E41 balance tube (euro) had those same two ports.