Vsv?

[ewurt]

I have a 6/74 40, and I don't have the Vacuum Switching Valve (VSV). I didn't take it off, and it looks like it has been absent for some time.
Do I need this, or is it just a smog item that I won't miss? If I don't need one, how do I hook up the vacuum lines from the carb, dist, etc? Right now the manifold has one port blocked off and the other to the dist. The carb has no connection or block on the diaphragm.
I am asking b/c I rebuilt the carb and am now searching for a possible vacuum leak.
Any advice would help. Thanks.

 

[Stone]

***

 

[Stone]

<EDIT>DUH! I saw "VSV" and automatically started thinking "diesel"...oops. Ignore my posts.

 

[IDave]

Certainly my 71 came with a VSV. But it came without a speed detector and the speed marker had been cut off. That being the case, when I realized I would have to rebuild the carb, or replace it, I chose to go with a NonUSA carb so I could s***Can the VSV. You CAN just port the vacuum from the carb plenum to the throttle positioner, and from the PS carb base to the dizzy advance. That's the way the nonUSA carb is set up. But the carbs that were built to work with the VSV are a little different from the nonUSAs, so they may not be at their best.

Your 74 VSV system will be a little different from my 71, but probably basically like this, from the Emission Control Manual.

 

[Pighead]

The VSV is a smog item that you won't miss. I've got a pair of 12/'74s (Kalifornia).
Both carbs have 2 vacuum hoses at the base. One right next to the idle mixture screw on the right side of the carb, the other on the opposite side, in the base, just under the throttle linkage bracket. The one on the right goes to the dizzy, the one on the left goes to the throttle positioner (if you've still got one). Plug the one on the manifold or use it for a vacuum gauge.

 

[65swb45]

If you're running a stock 74 dizzy, then it's a vacuum retard, and it should either be hooked up to the outboard side of the carb [the secondary] or disconnected altogether. You will notice an improvement just by taking the dizzy off the intake manifold, which leaves it in a constant retard position!

 

[Pighead]

Ooops. Right. Forgot.
I'm running '68 dizzys...