Identifying vacuum accessories Z24(s) engine

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
Posts: 12
Joined: Wed Aug 13, 2014 9:38 pm
Car: Xterra(s) (multiple), 720 Pickup


Hi all -

I'm attempting to correlate all the vacuum (controlled) devices in the engine bay of the Z24(s) engine in my '85 720 pickup. There is a lot of terminology for each of these devices that could be different names for the same part and I'm hoping to get clarification.

I did find a vacuum diagram for a 1984 Z24 engine, but my engine bay has a couple other devices I can't identify. I'll post a link to that diagram below.

This is some of the items I have in the engine bay, that I'm wanting confirmation on (in order to ensure the vacuum lines are correctly routed:

1. EGR Valve. I know this is an exhaust gas recirculating valve. There are other "EGR" devices I think, such as controllers, switches, etc. that I will attempt to identify as well.

?? 2. VVT Valve. This is NOT a variable valve timing valve. Google searches on "VVT with EGR" do not reveal the true identity of a VVT valve. The Haynes manual discusses it briefly, but just how to test it...not WHAT IT IS. :) What is this device? Is it the big "valve" looking thing next to the EGR valve? It is attached to the EGR valve by two lines. One from the bottom of the VVT (larger vacuum line) and one from the top (smaller). There is a third port on the top also, but it is capped off. ??

3. TVV. Thermal Vacuum Valve. I think I correctly identified this...installed in a water jacket (or something coolant related) in the intake manifold or a water neck right up front below the carburetor. Three port vacuum device.

4. Vacuum advance on the distributor. I was able to identify this, attached to/near the underside of the distributor.

?? 5. Vacuum control valve (*2). The " *2 " is indicated by a footnote, suggesting this device does NOT exist on "MPG" models or "Heavy Duty" models. I don't think I have "either" of those models, but I don't know how to tell for sure. Is there a third version in between that I might have? WHERE IS THIS DEVICE LOCATED? It looks like a two port device, and "could" be a small white "canister" looking device right up front in the engine bay, attached by a thin metal clasp to a bracket near the passenger-side of the valve cover.

?? 6. Boost control valve?? What the heck is that? I have boost control valves on my turbo cars, but is this terminology referring to something else more commonly? Is it referring to the above Vacuum control valve? WHERE IS THIS DEVICE?

7. AB VALVE. I think I figured this out, based on the shape of the device. It looks very similar to the image in the attached document. It's a gold-colored valve installed right up front in the engine, "under-ish" the carburetor. WHAT IS THIS VALVE FOR?

8. & 9. I think I identified these two "switches", though I don't know which one is which. There are two similar looking-shaped devices (and by "switch", I assume it's an electrical and vacuum device) installed onto the top of the inner fender liner (apron, skirt...whatever it's called) on the passenger-side. The image suggests (with a footnote), these are only installed on vehicle that are NOT either MPG or HEAVY DUTY models (or both).

?? 10. Near the above vacuum switch on the inner fender liner, there is a device that is a two-port "switch". Two vacuum nipples and one electrical connector. WHAT IS THIS DEVICE? I found that same device on an '86 truck with the Z24i engine (TB fuel injected), but it was actually located right up front of the engine, similarly attached to a bracket like device 5. above, if I correctly identified that.

That's a decent start to the items I have on this engine. Any help would be appreciated. :)



Posts: 8
Joined: Tue Dec 28, 2021 5:56 pm
Car: 1982 Datsun 720


Can you send me a picture of where the ab vavle connects to?!?’

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