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Down in flames.
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Discussion Starter · #1 ·
Back in the 60s and 70s, some high powered cars had cowl flaps, hood flaps, ram air flaps, or air filter housing flaps that were controlled by a vacuum valve. As the throttle opened, and vacuum fell off, the valve would open the air flaps to let in more air. Does anyone know the exact name of the vacuum valve that was used to control those air flaps? When I look up vacuum valve, I get all kinds of weirdness. I think they were commonly known as vacuum pull off valves, but that search term returns weirdness too.

What I am trying to do is control the control secondary intake air valves in a Ford 4.2L with split port heads. I've seen guys used MSD RPM pill boxes and have the valves fully open at a set rpm using the OE stepper motors. I'd like a little more control over the secondary air valves for the EFI system I'm planning to run. I want to keep it from having problems with a sudden change in vacuum.

You can see the secondary air butterfly valves in the outside ports of the lower intake from a 4.2L. This is on the head side.
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Old(s) Fart
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Most of those installations didn't use a valve. They just connected the vacuum actuator directly to manifold vacuum. The diaphragm in the actuator held the device closed when vacuum was applied. At wide open throttle, manifold vacuum drops to zero, releasing the actuator and opening the device. Newer cars have a lot of vacuum operated electric switches for various emissions controls. If you need an electric switch, your best bet is to get an adjustable Hobbs switch.
 

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Down in flames.
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188 Posts
Discussion Starter · #3 ·
Most of those installations didn't use a valve. They just connected the vacuum actuator directly to manifold vacuum. The diaphragm in the actuator held the device closed when vacuum was applied. At wide open throttle, manifold vacuum drops to zero, releasing the actuator and opening the device. Newer cars have a lot of vacuum operated electric switches for various emissions controls. If you need an electric switch, your best bet is to get an adjustable Hobbs switch.
Thanks! Actuator! That's the word I was thinking of, but couldn't remember it. All I could think to call it was a valve. I need the vacuum style actuator. I found many turbo vacuum actuator's for around $20-30 that will do what I need done. I don't need a turbo thankfully. Thank you again.
 
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