Hi,

 

I have '75 280z and it comes with nice big pet-bottle style vacuum tank. I wonder whether I can just swap this with 280zx smaller size vacuum tank with valves to save space and clean up.

 

 

swap with 280zx vaccum tank.

 

Do you think there is any problem?

 

Thanks,

tamo3

It should work. Only problem I can imagine is a shortage of vacuum if you play with the AC controls too much.

You could check the size of the vacuum servos on the 280ZX and compare them with the ones in the 280Z. They might be smaller and therefore requiring a smaller vacuum tank.

If the vacuum does run low it can effect your fast idle and the engine speed will drop and could even stall.

 

Certainly clean up that side of the engine bay. Its small enough to mount between the dryer and the carbon canister.

Chas

I agree and have considered the same modification. I like the 280ZX version because it's got the solenoid valves built into it.

 

The only time the vacuum does anything when the system is in transition. When you push a button and change a position, it'll consume vacuum, but once the transient has past and everything has reached it's new desired position, the draw out of the tank should stop.

 

I'll differ from Chas above and say that the only time there would be a problem would be when you play with the controls WHILE you are at full throttle and don't have enough manifold vacuum to refill the tank with vacuum as you consume it. (Negative sense on the "refill" or course... You know... "Refilling a tank with vacuum??"  )

 

It would be worth testing, but I bet it'll work fine. You can get all the testing stuff worked out before I get to installing A/C!

OK, thanks for your feedback!

I will be 人柱 JINCYU (tester)

Excellent. I don't expect any issues.

 

The only difference I can see between the two systems is that the Z has the vacuum sources for the two solenoid valves in series, while the ZX has them in parallel. Shouldn't matter though since the only time the FICD is actuated is when the system is calling for A/C. Not sure why they put them in series in the first place.

 

Glad you'll be looking into this. 

My AC vacuum source suddenly died. I traced it to the vacuum check valve. Don't ask me why but for some reason it works in reverse now. that's right it will NOT allow air to flow FROM the tank, but will allow air to blow INTO. So odd. I can reverse the valve and it will work as designed. I have no idea how the one way valve can suddenly reverse. If anybody has one of these let me know. Can you suck air thru the big end but not the little end. I am going nutz over this.

Hey, I just did this swap a couple weeks ago!  I kept the old 280z check valve, but I can double check it when I'm at home if it's any help.

14 minutes ago, charliekwin said:

Hey, I just did this swap a couple weeks ago!  I kept the old 280z check valve, but I can double check it when I'm at home if it's any help.

It could save my sanity, on mine the air flow is from the small side to the large side, that is I can blow air thru small side where the metal retaining washer is fitted to hold it in place.

I am going to hit that MOFO with some 100 PSI and see how it likes that

I'm not sure how helpful I'm going be, but here goes: here's how the check valve is positioned in mine, with the wide side towards the vacuum source.  That's how it was set before I swapped the tanks.  I blew into both ends and air wants to flow from the wide side to the narrow side, but that seems like it might be backwards, AND I now believe the valve has gone bad, because it does flow *both* ways -- just maybe half as much the other way.  All that said, the HVAC controls still work, but looking at the first post, I'm realizing now that a check valve is integrated with the tank itself, so the one I have pictured below is probably just acting as a coupling.  So...uhh...you're welcome?

getting odd, on mine the air flow from the narrow side (bottom of your pic) to the wide side (top of your pic) that is you can blow air into the bottom and it will flow.

On mine the narrow side (bottom of you pic) was trapped by a lock washer to the frame that holds the magnetic valves. This narrow side was then connected to the source of the vacuum thru a vacuum line that was tape together and routed back to the intake manifold. the Wide side (top) was connected to the bottle. I have added the pic of the way mine is installed, this is from another poster a few post back

Edited September 23, 20168 yr by Dave WM
added pic from a few post back

I moved the check valve (which I now realize was unnecessary) when I swapped in the ZX tank.  It was originally located up by the bracket like the photo above, but didn't have a retaining washer.  Given the provenance of my car, I wouldn't be surprised if it had be futzed with.  HVAC mode switching didn't work prior to swapping tanks, either.