EFE-TVS / Ported Vacuum Switch HELP!?!?

[teamcurtis]

1978 C10 350 in California

I recently replaced the water pump, and intake manifold in my C10. The EFE-TVS was helplessly rusted into the thermostat housing and had to be replaced. Ive got most everything buttoned up now and I'm working on all the vacuum lines. The truck did pass smog before i bought it, but I have little faith it was hooked up correctly.

I could not find a EFE-TVS that looked the exact same. At auto parts stores a 78 C10 is always listed a 3 port switch. The schematics from the service manual and what came off the truck is a 4 port. I found Stand Motor Products PVS81.



So my real issue is that the diagram shows 4 ports all on top of each other. The switch i got has the bottom two side by side.
Is this switch gonna work? How do I hook this thing up correctly?
(it has 2 charcoal canisters)






Please don't reply with comments around how useless SMOG laws are or "that's why id never live in CA" 

[bd]

Post a pic of the TVS, looking directly into its vacuum ports.  Typically, none of the ports share a horizontal plane, but are offset vertically, at least slightly, along the switch long axis.

[bd]

Ha!  That was fast! 



Notice the subtle vertical offset of the lower two ports.  The lower left port is the bottom port in the schematic and the lower right port is the second to the bottom port in the schematic.

[teamcurtis]

thanks guys!
hopefully this rain will stop long enough for me to run new vacuum lines!

[bd]

You're welcome.  I believe the OEM part number is 3039144.  You might try doing an Internet search.

[teamcurtis]

Which actually yields the one i got...

https://frugalmechanic.com/auto-part/oem-3039144-ported-vacuum-switch?p=frugalmechanic_google&gclid=CPvz06v-2NECFYpffgodGmIDBg

[bd]

Well, there you go.  Now you can feel confident it's right.  If you reside in California, print off and keep any research documents as backup in case the smog cops try to hassle down the road.

[teamcurtis]

good tip...
ok thinking thru this while at my desk at work...

the vacuum port(s) on the manifold itself.
what should these be hooked up to? Brakes? heater?

[bd]

A pic of the manifold vacuum fitting would help formulate a more definite response, but from memory:

• 11/32" nipple to vacuum brake power booster
  
  
• 1/4" vertical nipple to automatic transmission modulator valve steel line
  
  
• 7/32" (if there is one) to heater/AC vacuum reservoir

[teamcurtis]

that sounds spot on as the fitting for that port in the intake had a 3 hose tree on it.

ok here is another one for you.

"G only"?
I see in other schematics C truck only, which is 2wd, but i dont know what G signifies

[bd]

"G" is GM's shorthand for the full-size light duty vans.

[teamcurtis]

Got most of this plumbed last night. needed a few strange Ts and Ys as multiple size hoses join together.
How this passed smog with the canisters hooked up wildly incorrectly is beyond me.