So, my engine has this crankcase breather tube and while it's capped off, it certainly looks as though it had an outlet that got broken off; possibly when the engine was shipped to me some years ago.

I know I need to route this outlet to somewhere on my Canon intake manifold (triple Webers) but one question is how to do that? I'm thinking I'll just cut the tube inboard of that hole and attach a brass nipple for the hose leading to the intake manifold. Sound reasonable?

Also, I presume I still need to put a PCV valve somewhere between the outlet tube and the intake manifold. Right?

Datsun spirit capped mine off with a freeze plug. You can either run a K&N filter attached to the valve cover outlet or run a hose from there to a catch can.

Edited May 4May 4 by Yarb

What dizzy is that @Yarb ?

With your outlet sealed off, how does internal block pressure get relieved? Admittedly, at an engine temperature of 212 F it's only about 4-5 psig overpressure, but your pistons will have to work against that on downstrokes.

Through the timing cover up into the head and out the valve cover port. Just like old school cars that had a vented oil fill cap.

@Patcon That’s the 123 distributor

Edited May 5May 5 by Yarb

10 hours ago, Yarb said:

Through the timing cover up into the head and out the valve cover port. Just like old school cars that had a vented oil fill cap.

@Patcon That’s the 123 distributor

Would be interesting to post your spark curve up in a different thread at some point and the engine specs.

Sorry for the thread jack...

OK, Yarb, that makes sense. I'd forgotten that the front main seal leaves a lot of space around the crankshaft opening. So then, three questions.

1. How much oomph does it take to remove that breather tube?

2. Is there a best procedure for removing it, like hitting it with a mallet?

3. What size freeze plug do I need to get?

It’s just pressed in. Rotate left & right to break old paint and rust. After you’ve gotten it to some point of loose, continue the same motion and start pulling it away from the block. There’s a lip on the end of the tube. Not too large but enough for it to be a pain.

As far as the freeze plug, just mic it out for measuring the size. Google it and you’ll find supplier availability.

I always thought the freeze plug was a terrible idea. I would vent it to a catch can, at least.

19 hours ago, Seppi72 said:

PCV valve

I think that "positive" crankcase ventilation came later. Where the system was designed to move air through the crankcase. They just called it "closed ventilation" before then. Meaning that the crankcase was connected to the air intake system instead of open to air. Anyway, wherever the exit from the crankcase ends up there will be oily gases at times.

The pressure comes from blowby past the rings. Maximum pressure would be at high RPM, high load. So you'd want to estimate how much blowby you might expect. If you plug the big port then all of it has to pass through the small port in the valve cover.

(p.s. core plug)

The intake manifold at least from my experience with OER does not have a provision for crankcase ventilation. Upon research I ‘ve found and recommendations from the builder is to go one of the two routes I mentioned earlier.