Vacuum Switch on Water Neck

[Stepperado]

My particular truck is an 84 with a 305/auto, but I know a lot of our trucks had these.

In any event, can anyone shed light on the inner workings of this switch? It's pretty obvious the water temp is controlling a few functions here, but I'd love to know what it's controlling and how.

Thanks,
Stepperado

 

[Green79Scottsdale]

Basically what I understand is that the switch controls the amount of vacuum available in relation to the coolant temp. Warmer temps means more vacuum available for the vacuum advance on the distributor.

I just removed all the lines that go to this particular switch on my 400sbc equipped '79. I also had a similar switch directly into my intake right next to the water neck that I removed all the lines from. Bumped the timing from the stock 4* up to around 11*, and the truck runs great now! I have a thread were I asked about vacuum lines and such and I plan on updating it this weekend with pictures and results.

Hope this helps you out!

 

[Stepperado]

I can see a temperature switch shutting vacuum on or off, but I have to admit it sounds like a stretch that they would use this switch to control the level of vacuum.

Hopefully there is documentation out there to back up a theory. I'd love to see it.

Oh, and glad you are happy with the way your truck runs. That's always nice to hear.