1 hour ago, Clark166 said:

Also i see you have a throttle cable. Did you custom make that or is that something that can be purchesed i really like that over the linkage i have right now

Custom made. Most of the pieces are from Venhill. The cam is from @duffymahoney. Drilling and tapping the stainless steel plug was the hard part. I’d use aluminum if I was doing it again.

On 3/14/2026 at 5:06 PM, Matthew Abate said:

Catch-Up Digest, Continued. After this I’m up to date.

•••

March 9, 2026

They said it couldn’t be done.*

If you have been following this project long enough (good job 👍🏻) you know this engine had SUs when I installed it. Lots of drama later I put triple Mikunis on it, and I’m glad I did.

One thing my euro-spec SU balance tube has that my short Mikuni manifold is missing (other than clearance) is a PCV valve. Around the time I got the triples working I installed a bracket to hold one with a plan to figure out how to connect it later.

Well, later is here. Several years ago I saw a Z at the east coast import show in PA sporting a custom air filter housing for a Lamborghini Countach air filter. The owners is here but I can’t find the name.

We ALSO discussed its balance tube on the manifold. My plan was to do something like that, but add a port for the PCV valve. (Nismo put one with a PCV valve on the l型6気筒 TLX manifold, so please hold the snark).

I would have liked to figure out a way to mount the valve right on mine, but routing the hose was getting too difficult. This cleans up the visible plumbing better. Hopefully it with function as intended.

My vacuum manifold also uses the port on the #6 runner meant for the brake booster, so I move that fitting for to the back end, as well. Eight ports in all.

It’s made from a 22.5 inch piece of aluminum pipe (1” OD, 0.25” wall for tapping, which is technically not enough but works). A buddy of mine was MVP on this for welding up the ends, getting my specs into his CNC machine to bore all the holes, and letting me use his lathe and mill to start the guide taps.

A quick media blasting with aluminum oxide and it was pretty simple to install. The hardest part was getting 1/4” stainless tubes bent to the right angles to accommodate the irregular angles of the six manifold ports, which are so irregular they must have been drilled and tapped by hand.

Lest I create the impression this was a complete breeze, know I finished a prototype meant to be final using a vacuum manifold, but bailed on it after the tubes started to look like a mess of spaghetti.

Pro tip: if you’re doing something like this, get some copper tubing at a hardware store and mock it up with that before you start bending stainless.

I’m pretty happy with this. The only thing I would change is to use thinner walled stainless capillary tubing. This stuff is unnecessarily robust, so it’s hard to bend and a smaller inner diameter than it could have been.

*I don’t know how the balance tube will change how the engine runs. The assumption is slightly smoother, with the brake vacuum building faster at 6 times the frequency.

•••

March 11, 2026

Nearly done in here.

I picked up these Kameari stainless air filters on a whim from JDM Car Parts a while ago, and I’m glad I did. They look really nice paired with the heat shield (also from Kameari). I was nervous the shield wouldn’t fit with the cooling blocks installed, and it is tight, but it isn’t touching them or the header so I think I’m good there. The braided cooling block lines look nice over that shiny stainless steel.

I’m still debating whether to get some short velocity stacks that will fit inside these filters. I do have a plenum for a cold air intake, and I think the old stacks are short enough to work in that, but I think it’s going to be a while before I get to that.

Everything is back where it belongs now, except for the throttle cable and the booster hose. I remade the cable bracket out of thicker gauge stainless to get rid of the flexing problem with the previous version. As such I need to make some adjustments to the cam (and replace the barrel nut I lost). The hoses I need to reroute and trim to connect to the vacuum manifold I just installed.

Otherwise I just have the windshield wipers and water tank to put in here and I’ll be pretty much done inside the engine bay.

Well done dude! I never got PCV and ITB to play nicely. Caused almost a vac like leak. The issue was my idle ended up too high for my liking. So I ditched it. I am going to give the exhaust method a shot.

3 hours ago, duffymahoney said:

Well done dude! I never got PCV and ITB to play nicely. Caused almost a vac like leak. The issue was my idle ended up too high for my liking. So I ditched it. I am going to give the exhaust method a shot.

Well, I’m not totally sure it’s going to be all sunshine and rainbows yet. I haven’t taken it on the road yet. The idle is definitely low compared to before I put it on. No verdict on how it effects the brakes.

@duffymahoney ,

You’re right. Mimics a vacuum leak.

I have a theory about what’s going on, or at least why it doesn’t do what the balance tube on the SU manifold does.

With this, you have all three intake runners connected, so each intake stroke is open to five other runners. With the SUs, the balance tube isn’t on the six intake runners but is up before each half splits into three, so in that case it’s balancing three with three, rather than one with five. In other words, it balances 1, 2, and 3 with 4, 5, and 6. This one tries to balance each individual runner with all of the other five, so you have to have way more vacuum as a result. Maybe narrower runners and a smaller internal balance tube volume would make it work, but I doubt it.

I thought initially it would be the PCV valve causing the problem but it didn’t change when I plugged that port. I’m going to save the PcV valve experiment for a later date when I move to a cold air intake. I think putting it on the back of that, the same way the valve cover vent hose is on the SU air filter, would be the only way to do it without expert engineers figuring it out.

I’d like to know how they made it work on the new Nismo head, though.

Have you put a vacuum gauge on the balance tube to see how the vacuum looks? I'd try it at both your more centralized PCV connection, and also at your brake booster connection on the end.

Just to see if you can glean any useful info from the gauge?

3 hours ago, Matthew Abate said:

@duffymahoney ,

You’re right. Mimics a vacuum leak.

I have a theory about what’s going on, or at least why it doesn’t do what the balance tube on the SU manifold does.

With this, you have all three intake runners connected, so each intake stroke is open to five other runners. With the SUs, the balance tube isn’t on the six intake runners but is up before each half splits into three, so in that case it’s balancing three with three, rather than one with five. In other words, it balances 1, 2, and 3 with 4, 5, and 6. This one tries to balance each individual runner with all of the other five, so you have to have way more vacuum as a result. Maybe narrower runners and a smaller internal balance tube volume would make it work, but I doubt it.

I thought initially it would be the PCV valve causing the problem but it didn’t change when I plugged that port. I’m going to save the PcV valve experiment for a later date when I move to a cold air intake. I think putting it on the back of that, the same way the valve cover vent hose is on the SU air filter, would be the only way to do it without expert engineers figuring it out.

I’d like to know how they made it work on the new Nismo head, though.

I think if the throttle blades close enough at idle, allowing pcv to function it could work, but then they would tend to stick. Maybe the SU's close off more? I have a patented stack filter, that I am working on, that if done correct, it would be a great place for the pcv to go.

I never found a balance of non sticking throttles and working pcv.

8 hours ago, Captain Obvious said:

Have you put a vacuum gauge on the balance tube to see how the vacuum looks? I'd try it at both your more centralized PCV connection, and also at your brake booster connection on the end.

Just to see if you can glean any useful info from the gauge?

I noticed I’m having some brake issues so I retired the balance tube for now. Once I get some of the must do things knocked out I’ll revisit it. It looks nice in the box, though. 🫩

14 hours ago, Matthew Abate said:

I noticed I’m having some brake issues so I retired the balance tube for now.

You think the brake issues are related to the balance tube?

What are you doing instead for brake vacuum if you aren't using this balance tube?

I reconnected the hose to the number 6 I take runner port, which is where I had it before.

Right now I think my brake issues are being caused by air in the system, specifically in the MC. I’ve bless it three times and, even though the pedal is nice and firm when I finish, by the time I get it back on the ground it’s soft again, boost or no boost.

I also noticed my rear calipers are getting a sheen of brown so I am going to pull them to be painted since I’m going to have to bleed this thing again anyway.