Yes I will try setting it just with the idle screws and not have the linkages interfering.

I'm an experienced hose listener.!!! I've had su's before.

I was wondering if the carb would be running high or low if there was a major air leak.

I think it is supposed to stay open, pulling a slight vacuum in the crank case. It closes if/when there is a backfire in the intake.
As I understand it the benifits are... less emissions...better ring seal...less external oil leakage.

I have found that there is nothing wrong with the PCV valve - it functions - and when blocked off seems to make no noticable difference to the engine running.

The spring is present but is very slack. I put hose clamps on the hose from the block to make sure we weren't leaking any air - and its all cool.

Ah, the old-fashioned vacuum leak. Good to know that this was the cause.

I saw that competition engines do not use the PCV valve at all, I might go that route upon ridding my A15 from smog dvices soon. Also I read in Des Hammil 's book on rebuilding engines that the PCV system can work in this way. Connect both the valve cover hose... (hose from valve cover to carburetor) ...and block hose(hose from block to PCV valve)... to a single filter breather each, or one for both hoses(could even be a plastic bottle with small openings, I prefer the breather, has a filter element to prevent dust intake) . Both filters(if using a single breather filter for each hose) or the single filter(like a empi air cooled VW breather filter used in VW baja bugs)...or plastic bottle, have to be positioned at least as high as the highest hose, in other words, the breather(s) have to be as high or higher, not lower , than the engine valve cover . Do not connect a small breather filter to the block hose down there, below the valve cover height. The PCV valve then can be taken away and the port closed . This will give the car a cleaner carb (no oily stuff going in there, a tighter intake system,no burnt air going into the conbustion chambers via PCV valve, and direct clean cool fresh air into the crankcase when needed. The PCV valve is an emission device that tries to burn part of the oily stuff that comes out of the engine. 99% of vehicles have a PCV valve, but if performance is your goal, there must be a reason why racers do this with their system.
Jaime.
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Jaime.__________________________

PCV=Positive Crancase Ventalation, the reason it's there is to allow the crankcase to breathe.
think of it this way: for every bit of air that moves through the intake and exhaust manifolds, an EQUEAL amount moves through the crankcase. some of this being blow by past the piston rings.
the pcv system is there to allow fresh air to vent those gasses out of the crankcase, and the pcv valve is there to ensure that the air for venting moves in 1 direction only. the pcv valve is also designed so that if there is a backfire, that the flame will not burn back into the crankcase and cause it to blow up(yes it has happened) there is no bennifit or performance gain from disconecting or modifying the pcv system. there is a slight fuel milage advantage to having one that works because it will take unburned gas and feed it back through the engine. as far as getting oil through the hose into the intake, there is a screen baffle inside the engine crankcase to help prevent this, if one has an excessive amount of oil passing through, then the rings are worn and should be replaced.

Well I left mine on despite the odd noise it makes when the engine is not running smoothly - as posted earlier.

I think it is far more elegant to just push the crank fumes back into the motor as intended.

Hy bro. The PVC or positive cranckcase ventilation is designed to ventilate the engine, that I agree. It does not go in one direction only, that is not right. When driving at slow speeds, engine idle, it goes the path we all know, new air(not new, bad air from the block into the PVC valve)...or contaminated air from block into intake system via hose through PCV valve, and into the engine via air cleaner assembly through hose into valve cover. At high RPM, fast speeds, full throatle, the PCV valve and intake manifold can not absorb the amount of gases that the engine is producing, so the air demands of the engine, demand to excrete this bad air out of the block that normally goes out throgh the block opening into hose and pcv valve into intake will now exit the engine the other way, through the valve cover INTO the CARBURETOR, sending bad air, with low amounts of OXIGEN, full of burnt hydrocarbons into your intake and combustion chambers, not very good nor healthy for your engine, which needs oxigen, not burnt hydrocarbons. At high speeds the block goes into a release mode, needs to get rid off lots of hot burnt gases/ heavy air.By having both exits (block to breather against block to PCV valve, and, valve cover to breather against valve cover to carburetor)... connected to breathers, you asure fresh air into the engine when the block sucks in air(lower speeds, iddle,block takes in air and also releases air), instead of burnt hydrocarbons, and no burnt hydrocarbons into intake system through the carburetor hook up to valve cover. The reason to route this bad air into the carburetor is to burn and re burn these gases before they go into the atmosphere. Since very few of us in the world are looking to make our Datsuns perform well, we are not making any major pollution problems to this world,Very small minority) for that reason,(to see a polluter in progress) drive behind a diesel vehicle and see what pollution is all about. The engine only needs to release all this by product of engine work(gases) out of the block at high speeds, and will take some fresh air at slower speeds, that is what the breathers do, you do not need a PCV system, only a ventilation system for the block, which the breathers do,the intake and burn of this gases is an extra thing not needed for best performance and lasting of your nice expensive carburator. Without the PCV valve, your performance should get better because you do not have gases burnt with no oxigen content invading the space that clean air mixture should be taking inside your intake and combustion chambers.Nor you would have oily gases with no oxigen mixing with gasoline/petrol in your carburetor as a consecuence of this valve cover hose releasing this bad burnt hydrocarbon air into your carburator, space fresh cool air could be using. Imagine a cold air box designed for your car, you want colder air to reach your carburation for proper performance and excelent mixture in the carburetor, then, why would you sabotage all that excelent work(cold air box, ram air) with some hot burnt hydrocarbon saturated low in oxigen air also oily and messy, into the mix?
Think about it, you do not need that bad air,and it will not pollute nothing.The PCV valve is a re burning device (re burning of bad air) , not a necesity, I would say a luxury not needed.

Jaime._____________________________

Jaime, you should read an auto mechanics book to get the real scoop on PCV system. Yes, you don't need it, your engine will run OK without it -- but that doesn't mean it is evil. And although it was originally designed for emissions control, it does have some benefits other than emissions.

Jamie,
I second that statement, I teach this stuff every day. More to the point, I have delt with emission controlls for over 30 years.
honestly, it sounds to me as though somewhere you have gotten some information that is incorrect.
as an aside, before there was a pcv system, engines had what was called a road draft tube. basicly this was a tube about an inch in diameter that hung off the side of the engine, ending at about the bottom of the oil pan. oil caps were vented to allow fresh air in and the crankcase gasses vented out the end ot the tube, it took them a while to figure out that all that oil all over the bottom of one's car came from that road draft tube.