Am I looking at a monster vacuum leak here?

[ArcticFoxCJ]

Got my intake manifold back from the machine shop, and the EGR gallery has corroded so thin you can poke through it with a screwdriver.

I have a sinking feeling this manifold is toast, but with a flashlight in it I can't tell whether the ports between the EGR gallery and the intake are open.  Anyone have any insights?

[Yarb]

Try to find I believe a N42 manifold from a 75 model Z.

[ArcticFoxCJ]

1 minute ago, Yarb said:

Try to find I believe a N42 manifold from a 75 model Z.

OK, what's the advantage to an N42?

[Yarb]

Non-EGR intake.

[ArcticFoxCJ]

1 minute ago, Yarb said:

Non-EGR intake.

Gotcha.

At this point if I can use this one I will, since I'm deleting the EGR anyway.  The only question is whether there's airflow between that gallery and the actual vacuum chamber.  I tried to run a wire through what seems to be a port for cylinder #1 but it appears to be blocked.  If that's the case, then this manifold is usable.  

I could try to pull out the hex plugs and see better, but I'm nervous about putting all that force onto them, since they're on pretty tight.

[Terrapin Z]

Shameless plug 😎: I have a few manifolds if you end up needing another one.

[SteveJ]

6 minutes ago, Terrapin Z said:

Shameless plug 😎: I have a few manifolds if you end up needing another one.

I'd say that's less like a shameless plug and more like a helpful offer.

[siteunseen]

Judging by one of your pics all that black soot around that jagged hole confirms exhaust is going through the egr tunnel.

I had a golf ball size hole in my n47 from exhaust gas rot.

If you don't have to deal with the state inspection I would highly, highly recommend going to an n42. 

[Zed Head]

I've removed one of those plugs.  It's not too difficult.  Heat the metal around the plug before putting the torque to it if it's stuck.

Can't remember what I saw but I assume that the hole in to each runner is right below the plug.  You could drill and tap each runner port and put a screw in it.  Wouldn't be too hard to do.  The alternative is more patching and welding or gobs of JB weld.

[ArcticFoxCJ]

1 hour ago, siteunseen said:

Judging by one of your pics all that black soot around that jagged hole confirms exhaust is going through the egr tunnel.

I had a golf ball size hole in my n47 from exhaust gas rot.

If you don't have to deal with the state inspection I would highly, highly recommend going to an n42. 

Yeah the soot is from the welding attempt.  I do agree that EGR was getting in previously, but I am deleting the EGR so I'm not worried about whether it was working.  Looks like finding an N42 is an adventure...

53 minutes ago, Zed Head said:

I've removed one of those plugs.  It's not too difficult.  Heat the metal around the plug before putting the torque to it if it's stuck.

Can't remember what I saw but I assume that the hole in to each runner is right below the plug.  You could drill and tap each runner port and put a screw in it.  Wouldn't be too hard to do.  The alternative is more patching and welding or gobs of JB weld.

Yeah I was thinking along those lines as well.  Managed to get one plug off and check this out:

 

It's jam packed solid in there.  I don't even know what this material is.  It's almost like sawdust.

Judging from some damage on a couple of the plugs, I'm starting to wonder if someone had already done that to this manifold before...

[Zed Head]

I found sandy material in mine also.  I thought it might be carbon residue from exhaust gases, but maybe it's actually casting sand.  Might be that Nissan found that it doesn't pass through to the intake runners so no need to clean it out.  Who knows.  

Did you poke through to the runner?  See if the port is visible.

[ArcticFoxCJ]

8 minutes ago, Zed Head said:

I found sandy material in mine also.  I thought it might be carbon residue from exhaust gases, but maybe it's actually casting sand.  Might be that Nissan found that it doesn't pass through to the intake runners so no need to clean it out.  Who knows.  

Did you poke through to the runner?  See if the port is visible.

yeah I dug out a bunch more of the material.  This is what it looks like at the bottom:

 

That's aluminum in there.

So either this has been plugged, or that really was casting sand and Datsun was cheating a bit when manufacturing these...

So... if they're all like this, then I can use this manifold.