Might be that those aren't access points for the EGR ports but are actually core plugs.  Screw-in instead of the typical press-in.

I've never examined the inside of an intake runner to see where the exhaust gases are let in.  Might tell you something.  There has to be holes somewhere.  I've seen them on my 2003 vehicle, a Ford.  They're known to clog.

The FSM is pretty vague with magical arrows.

Edit - actually I think that the holes are in the plenum not the runners, I think I knew that but had forgotten.  Harder to see.  Which I still had my pile of parts to go play with.  A borescope view would be fun.

Edited October 28, 20231 yr by Zed Head

N42 Intake!! Call it a day.

Found a thread about a turbo ZX manifold.  The ports seem to be right at the entrance of the runners.  Seems like you should be able to see more in yours.

https://www.zdriver.com/forums/280zx-s130-forums-77/my-turbo-plenum-32430/

6 minutes ago, Yarb said:

N42 Intake!! Call it a day.

Don't ruin the entertainment man.  The day is long...

So I am able to feel one of the ports with my finger on the throttle body end, and when trying to push a bent wire down through to see if it was clear, I was unable.  Here's what it looks like from the throttle body port (second pic is zoomed in)

 

Thanks.  It looks like they shaped a slot instead of a circle.  You might try compressed air if you have it.  

But, if you can see the backside of the slot, maybe six gobs of epoxy will seal things up for certain.  SteelStik is good stuff.  Quick, cheap, easy, rock hard when it cures.

https://www.jbweld.com/product/steelstik-epoxy-putty-stick

 

5 minutes ago, Zed Head said:

Thanks.  It looks like they shaped a slot instead of a circle.  You might try compressed air if you have it.  

But, if you can see the backside of the slot, maybe six gobs of epoxy will seal things up for certain.  SteelStik is good stuff.  Quick, cheap, easy, rock hard when it cures.

https://www.jbweld.com/product/steelstik-epoxy-putty-stick

 

Thanks.  yeah to access the other ports I'll need to get the other plugs out.  Seems like my 10mm hex bit is just a little too small, so I have an 11mm impact coming tomorrow and I'll get out the rest with that.  I think if any of the ports are open I'll block them off to save the manifold.  I'd hate to waste the money I already spent at the machine shop on this one.  Not a sunk cost fallacy if I can actually save it.

For the trouble and pain it is to change out. Do yourself a big favor and replace it with a N42. What was the goal of sending it to the shop. Just EGR removal? If that’s it you are much better off getting a N42. These engines are fun to find vacuum leaks anyway. No doubt I’d change it out. I’m sure you can find something reasonable here on the forum. IMO of course.

16 minutes ago, Yarb said:

replace it with a N42

Post up a link to one for sale.  That would be helpful and show how easy they are to find.  Pick the best of the many that are available and fork out the small change.

Edit - I guess I'm saying that they're not as easy to find as you're implying, and when you do find them they're not cheap.  The N42 is the most popular of the EFI intake manifolds.

Coincidentally, many people think that Nissan added the webbing to the 1978 manifold to combat the heat soak problem.  Subject of a current discussion.  I'd look for an N47 (I think) 1978 manifold.

Still not cheap.  $8 for a tube of SteelStik.

https://www.ebay.com/itm/385520584919?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=So6yfmz_TvS&sssrc=2047675&ssuid=bBzFtXzvTQO&widget_ver=artemis&media=COPY

Edited October 29, 20231 yr by Zed Head

7 minutes ago, Zed Head said:

Post up a link to one for sale.  That would be helpful and show how easy they are to find.  Pick the best of the many that are available and fork out the small change.

I checked eBay and found no N42 Non EGR's currently for say or sold. I checked some other individual sites and they all said sold out. 

2040-parts.com list one for $500 but the site looks shady to me. 

Another on Instagram, also $500. beware of scammers!!

Those plugs cover over a passageway between the EGR passageway and into the individual runners. That "sand" you poured out is probably just years of decomposed aluminum and combustion byproducts and debris. If you removed one of the threaded plugs, you "should" see the hole up into the cylinder runner. And again, if you don't it's because it's all plugged with crap. It's there.

How do I know all this? Because I did an EGR delete on a ZX intake manifold. It was not a simple job. Went like this:

Step one was getting the plugs out. First one came out with no significant drama. Kinda like yours. Lulled me into a false sense of security. Just like yours.

Next couple required torch heat and an impact to get them out:

Next couple stripped out the hex (just like yours) and required emergency measures:

But if you manage to get all the plugs out, you should be able to look down inside the holes and see the passageway into the runners. Here's an example. Note that I've labeled the hole as 8mm, but be aware that they changed that later in the run and made the holes further from the EGR larger, presumably to even out the amount of recirculated gasses between the cylinders:

I drilled and tapped the holes and loctited a blug bolt into each of the holes. Then I sawed off the EGR section, milled it flat, and made a block off plate:

Quite a bit of work, but turned out great, and since the sealing into the runners is done with bolts, that plate doesn't even really need to seal.

I made two. One for proof of concept, and a second one since the first turned out so well.

Short story... I've got one available for sale if you're interested.