dalilama

I've been looking for the source(s) of my slightly rough idle and when checking the vacuum connections on the DVCS (1972 350 engine with factory intake) I noted that I could actually rotate the "tree" and I assume it is leaking air. I'm not sure if I could repair this and more likely I'll just eliminate it.

Any known way to repair this, and if not does anyone know what type of plug I'll need to plug the intake where I remove it?

joe_padavano

The DVCS is part of the transmission controlled spark emissions system. Distributor vacuum advance is disabled until the trans is in high gear. A switch on the trans operates the vacuum solenoid in the DVCS. Unless you care about correct appearances, you can remove the valve, disabling the transmission controlled spark system.

The decision to use either the original ported vacuum or straight manifold vacuum to operate the vacuum advance has spawned thousands of pages on the internet. I personally use straight manifold vacuum. The factory used ported vacuum. The problem is that since ported vacuum produces no advance at idle or light throttle openings, it can sometimes cause overheating at low speeds. Another function of the DVCS (and the reason why it screws into the coolant passage on the intake) is that if the engine starts to overheat, the thermally-controlled part of the valve switches the distributor from ported vacuum to straight manifold vacuum. This increases advance at small throttle openings, allowing the engine to run cooler.

You might ask yourself why that's not a good thing to have happen all the time...

In any event, if you continue to use ported vacuum for the advance, you need some sort of thermal vacuum switch to prevent overheating.

Macadoo

I eliminated my DVCS during the refresh, went with straight vacuum with no problem. I also bought a set of manifold plugs and it had one for the DVCS hole.
Good luck Brian.