Originally Posted by herring

Ok, first I have to say I was a little overoptimistic on my "cure". While it certainly did help things, the 1-2 and 2-3 shifts are still not smooth. The best I can say is that if I accelerate "just so" I can get them to be smooth...which is an improvement. And they're always smoother than before.

To recap, I've got a line coming directly off a large-diameter trunk line, which goes through a "Y" connector. One branch goes to the VCV (through the flying saucer), the other goes to the transmission. Where the 2mm orifice was (and where the 0.8mm orifice is now) is past the "Y" going to the VCV. So this has the effect of "diverting" more vacuum to the transmission.

I played around a bit today, putting the orifice on the "input" side of the "Y" (reducing flow to both the VCV and the trans). It made things slightly worse. I then removed the orifice altogether and capped off the line to the VCV, so 100% of the vacuum went to the trans. Very smooth, but no power due to being always in too high a gear, and slow shifts. Stupid me left the Mityvac behind so I didn't measure vacuum but now I have a sense of what's going on. Ideally, the trans needs more vacuum than it gets now, but not all that the pump can put out. IOW, an even-smaller orifice (if such a thing existed) to the VCV would be ideal.

I will still probably work on restoring the flow to the switchover valves on top of the engine. I did the puff test today, as far as I could. Again referring to the above diagram, this is part # 71.

Air blown in hole 1 comes out hole 3.
Air blown in hole 5 comes out hole 4.

This is at idle.

Hole 2 on my vehicle is broken off at the connector and capped off with a bolt on the hose side. This could be the reason my system was so "hacked".

Question: If I don't want the EGR valve anyway, it seems like there wouldn't be any reason to restore the hole 1/3 flow (which just goes to the EGR valve). Am I right on this? So what else does the switchover valve do?