[GoreMaker]

I'm looking to add a vacuum switch to my build to keep coolant from flowing through the heater core until the engine's sufficiently warmed up. There's a crapton of thermo vacuum switches out there, especially from Standard Motor Products, but finding the switching temperature and the normal state of these switches is nearly impossible. The only spec I've been able to find is for the PVS48, which has a switching temperature of 117f (that's a bit too low), but I can't figure out if it's normally open or normally closed.

Is there a place that lists these specs? Barring that, does anyone know of a specific switch that will actuate closer to 160f and is normally closed?

[Schurkey]

When I was looking for that sort of info, I found it in the Illustrated Buyer's Guide. Has photos and descriptions of the various part numbers, grouped by part type--all the distributor caps in one section, all the heater control valves in one section, all the thermo-vacuum switches in one section, etc.

Good luck finding a paper copy at a parts store any more. Maybe they're online now.

What are you hoping to gain by shutting-off the coolant flow through the heater core? Doesn't seem productive to me.

[GoreMaker]

Quicker engine warm up and no uselessly attempting to warm up the inside of the car if I accidentally leave it with the heater on. I have coolant lines from the backs of the heads to the front crossover, so I don't need the flow to the heater core until the engine is properly warmed up. Every modern car does this electronically, it's dead easy to accomplish mechanically. Just need the right vacuum switch

[Schurkey]

Originally Posted by GoreMaker

Quicker engine warm up

First Guess: You need a different thermostat.

Originally Posted by GoreMaker

no uselessly attempting to warm up the inside of the car if I accidentally leave it with the heater on

Shut the fan off. Even with no coolant flow through the heater core, having the fan run will still make for a chilly passenger compartment. So either way, the fan should be "off".

Might make more sense to route power to the fan through a temp switch, so the fan can't operate until the engine warms-up. But that also disables the defroster which--even with cool air--can help clear the windshield.

[GoreMaker]

Yeah don't worry about my motives, just answer the question at hand