OK I think I've figured out that the balance tube port is the PCV and should connect to the valve cover but I'm still not sure about the port with the blue cap. Thanks.

I just blocked mine off same as you have done , but it looks like it could have been a vacuum line for a brake booster.

OK, I can only speak of the 1200 GX engines here, but you are correct, the direction of the airflow through the engine is reversed in the GX. Air is drawn from the air filter assembly down to the pipe at the rear of the engine. It is then drawn into the crankcase, & up into the rocker cover. From there it passes to the PCV valve.

You will need to get filtered air into the pipe at the back of the block & to at least give lip service to smog laws, it will need to draw it from one of the filters on a carb. In times of crankcase emissions overload, the extra fumes travel back up to the 'clean air' side of the air cleaner, then is drawn into the carb & passed through the exhaust.
If you fit a filter to the pipe at the back of the block,there is a possibility that it will become wet with oil, then clog up with dust.

Hi Dodgeman.
Thanks for the info. I didn't know there was a pipe at the rear of the engine. I'll have to find that and see if I can hook it up somehow. I don't have a standard air filter assembly so I can't hook it up like stock but maybe I can kludge something up. MIchael

Quote:
This is the pipe at the back that I was refering to.

Dodgeman,
That pipe goes straight into the crankcase? How do you keep the oil from coming out of it? I dont' remember how it was hooked before. ALso, can you tell if the PCV valve is the correct "direction" for a GX setup? You said the flow is opposite in the GX setup but I don't know if my valve is designed to work that direction. Anyway I can tell? The problem is the valve was replaced by my carb rebuilder and he may not know much about the GX setup especially if it's different from most other setups. Thanks,
Michael

Michael
The only thing that changes is the direction of the airflow through the engine itself. In both cases, all of the crankcase vapour is still drawn through the PCV into the manifold & from your photo, this part is correctly installed.

In a [one carb] stocker, filtered air passes into the rocker cover, down through the engine, through a gauze oil separator that is at the entrance to the pipe at the rear, through that pipe & up to the PCV valve that is located on the outside face of the manifold at the base of the carb.

In the GX, filtered air passes down into the pipe at the back of the block, through the crankcase & upward to the rocker cover, then out the top & across to the PCV valve, which now faces upward, & is located in the middle of the manifold between the carbs. The same PCV valve part No. is used in both cases.

This photo shows the correct, original connection between the rocker cover & the PCV valve. I would not be surprised if this same hose was used on all GX models.

In my picture [2 posts back] you can see the PCV valve & a part of the hose on my GX inlet manifold too.

Thanks again Dodgeman. That makes sense - I was thinking the whole cycle went the opposite direction for some reason.

Do you think that hose is the "block to manifold hose" in this picture: http://datsun1200.com/modules/myalbum/photo.php?lid=7553
? P/N 11826-H2300? Maybe they mean valve cover and not block?

Mu Datsun 1200 parts book says that part No. 11826-H2300 is called 'Hose- Rocker Cover to control valve', & the illustration matches the description.
It is mis-described in the listing that you have.

The only thing that would resemble a "block to manifold" hose is the one on a one carb stocker from the pipe at the back of the block up to the PCV valve at the base of the carb.

If you can get one of these 11826-H2300 hoses, please see if you can get one for me also. Let me know by PM or e-mail & I will organise payment with you.

Will do - I'll check tomorrow. I'm within miles of the biggest Nissan parts supplier in the US. Thanks again
Michael