California NOX Exempt label
 

This label is on the inside of the original windshield of my '66 California Tri-Power /4-speed GTO. I was told by a previous owner that this California NOX "EXEMPT" label was placed on cars that met certain exemption rules at the time. He thought "Tri-Power" cars qualified for the exemption. Does anyone have any details related to these labels?

NOX Box
 

Dan,

I’m thinking it was a 70’s thing in California.
In order to pass smog you needed to attach this ugly item under the hood and connect as instructed on the box.

I saw many of these back in the day and I have this nice example from years gone by.

My ‘66 still shows the outline of this decal on the inside of windshield.
I found an old decal years ago and temporarily glued it to the outside as an example.
Also found several new ones on line too.

Chris

The Box
 

Ugly back then, but kinda cool today.

Back in the early 80s I went down to have my 68's annual smog test done at a local gas station. I figured I'd have to have the NOX device installed. The tech proceeded to do the visual inspection and announced that I didn't need the NOX device since I had a 'Ram Air' engine. Wink Wink. That was news to me but I went along with it lol.
Apparently RA engines were exempt from the NOX device.
He proceeded with the required smog test, and attached an EXEMPT sticker to the lower right windshield.

Chris,

I was hoping you would have knowledge of this! Of course you had a NOx box tucked away in your amazing parts stash!! Here is a document I just received via email on the topic. It is reportedly from a vintage California State Police vehicle inspection manual.

That is some crazy cool stuff there!! As a former EPA emissions instructor, I would love to know what was in that box and what it was supposed to do and how? The only practical way to reduce NOX in those days was to reduce combustion temperature. Running an engine rich would accomplish this but drive HC and Co emissions up. Very interesting, Thanks for sharing.

The internals consist of a 555 timer, op amp, transistors, solenoid valve. capacitors and resistors. The 555 timer senses the RPM and triggers a signal to activate the solenoid valve which closes vacuum port to the distributor vacuum advance canister. Below the set RPM, it bleeds vacuum from the atmosphere to disable the canister operation. The setup is not unlike the 70-72 TCS system.

If anyone has the instruction manual for the Electro Nox, please scan and post it. I'm interested in what Air Quality Products recommend for the RPM setting, similar to what the Carter 5600X instruction say.