Hi yall!  First post here.  I've been trying not to ask too many questions and research on my own before begging for help, but I can't seem to find this answer.  Other posts where close but not quite.  I'm rebuilding a '72 240Z (Feb).  The car wasn't running when I bought it, so I'm nervous to rely on previous owner's status quo.  The smog system was removed and the two hose spots I highlighted in red are were empty when I got the car.  Parts manual calls it a "hose pipe connector."  If I keep it open like previous owner had it, does that have long term effects on the engine?  Like can gunk find its way inside?  Do I install a hose just to cover them?  Or block off totally?  Any advice yall gave offer would be appreciated.  I want to increase my odds that the car will still be running 50 more years from now.  Thanks!

Is that from a Chilton or Haynes manual?  You can get the Datsun manual from this forum's Download area.  Linked it at the end.

That's your PCV system.  The big hose nipple connects to the little one.  You can find them on eBay or somebody on the forum might have one.  Here's an example.

https://zcardepot.com/products/crankcase-pcv-vent-hose-oem-70-74

If you leave them open the top one will cause carburetion problems and the bottom one will blow oil vapors all over your engine bay.

https://www.classiczcars.com/files/

I wouldn't cap them off on concern of pressurizing the crankcase and causing oil leaks

That's good info.  That diagram is from the carpartsmanual.com under the Emissions Control Device section. 

I did get the FSM from this forum.  It's so helpful.  I just didnt realize the diagram you posted was the same part. 

$40 for the correct hose is perfectly reasonable to me!  I'll do it

Thanks yall!

Don't forget the PCV valve at the carb balance tube. I've never seen a plated one like in your picture.

And the top of the vale cover hose goes to the back of the air filter.

WRONG INFO DELETED. 🤪

I think it's a connection for the air pump? I have forgotten and it's too cold to go look.

I've plugged that nipple on the filter with a rubber stopper meant for a chair leg. Thank you for that tip @jfa.series1

Edited January 20, 20241 yr by siteunseen

Here's a couple of reference pics for you.

This is the PCV - Crankcase breather hose in place and the valve cover - air filter hose hanging loose at the top.

In this pic the valve cover - air filter hose is connected. Look just to the left of the front carb and you will see a port on the back of the air filter with a black cover. That port is for a hose to the smog pump. When the pump is deleted, the air filter port needs to be blocked. That is the 1" chair leg cover that @siteunseen referred to.

Excellent.  Very helpful.  Thank you all!