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[Diamond Black Geezer]

I believe all the vac reservoirs do, yes 

[Webby the Bear]

You can check the vac resevoir by pulling off one of the lines... if it hisses its storing vacuum. if its not and it doesnt hiss (like mine was) then order a new one

ps, any idea what the needle should do? i.e. should it just sit there? is it likely to be bouncing around? presumably it will drop when you put a bunch of revs on etc?

[terry paget]

From memory, it reads good vacuum at idle, then as you create a leak by opening the throttle it falls until with throttle wide open it reads near zero.

[Webby the Bear]

Exactly what i thought TP

I presume the needle at idle should be steady though? if not does that clue you in to summat not right?

[chrisgixer]

Indeed, hence you need working vac tanks that hold vacuum during WOT. Or the vac system no worky. As Webby found on his.

But the first thing to look for on the  vac system is a worn through servo pipe from pas side of the plenum. They wear through if the clip holding the ac pipe away is missing or broken. The two then come together and rub.

All the vac pipes run off the servo pipe. So if the servo pipe leaks, performance will suffer if the multi rams don't open.

[Diamond Black Geezer]

What he said 

if you find there is rubbing, once you've sorted a replacement main servo pipe, try get a much large diameter short length of hose, split it lengthways and fit round either bit of pipework, just to act as a buffer between the servo and AC pipe.

[Elmstoneboy]

Well, I've done some checking. I Put the vac gauge directly onto the vac tank, the ram control side, and got a reading at tick-over of around 18 - 20" Hg just as Kevin thought, so no problems there. Reading was pretty steady at around 18" Hg after the engine settled.
Increasing the revs reduced it down to around 12 - 14"Hg. This was with the engine running free. I would think it would drop even lower if under load, less revs with wider throttle opening.
When engine was switched off vacuum dived to zero, Problem found.    Took the tank off, had a fiddle, but could not get the non-return valve to work, I could hear something rattle inside which sounded like a ball in a valve, but couldn't get it to seal.
I guess the valve is on the large input side or should that be outlet side as it's a vacuum.

So, any good working vac tanks about?             Although, it wouldn't take much to make an inline one.

[Elmstoneboy]

Vac tank with working valve now fitted, Wow, what a difference 
Going up a long incline with just enough accelerator to keep increasing speed, and you can
feel when the flaps open in the Ram, she just flies, and as for kick down, I now know what a
kick in the back feels like. Amazing difference. Just shows you need to keep every gadget working
as designed.
One point about the kick down, she seems to kick down before reaching the floor button  Not sure
if it's me not yet used to the improvement, or something wrong.
Too frightened to go any further on the accelerator to find out. Any ideas.