[BackagainLJ80]

Ok, 4K engine. What is this part?




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[watermouse]

Would be where the coolant temp sensor goes on the thermostat housing. Should probably have some wires coming off it.

[BackagainLJ80]

I thought that was over the other side?


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[watermouse]

Not sure then, sorry. I have seen some photos of the sensor in that position but also others with it on the other side.

[fordem]

Are you referring to the fitting with two prongs? It's probably some sort of thermally operated vacuum switching valve.

[bumstein]

It's a BVSV valve I believe. Part of the emission control system. What does it do? No idea

[Grags]

Called a Bimetal Vacuum Switching Valve.
On some cars it stops the Exhaust Gas Recirculation system or the distributor advance, or both from working when the car is warming up
There were so many versions of emission control systems it would be hard to say if that particular switch was actually meant to be there on that motor or if a different one should actually be there.
If you attach a line to one of the ports and suck or blow on the line when cold it should be blocked. When warmed up to around 50-60 degrees it should let air through.
If that's the case then hook up the vacuum advance to it and it will help the motor warm up faster by not allowing advance when cold and it won't do anything to hurt performance when warm.
I'm suggesting that because if any nosy transport inspector or RWC mechanic sees nothing on it they go "aha disconnected emission control = fail"
But if there's tubes on it going somewhere doing something they will likely say nothing and you are therefore cool.
I made a good few dollars in my trade days re-connecting emission control and replacing the real cause of gutless performance, the camshaft