This is the implausible but almost completely true story of Regular Production Option W-73 for the 1970 Pontiac GTO: driver-operated exhaust cutouts.
The Motor City’s muscle car movement of the ’60s and ’70s has generated all kinds of crazy stories over the years, and some of them are even true. The tale of Pontiac’s W-73 Vacuum Operated Exhaust option for the 1970 GTO might seem apocryphal, but it actually happened. Pontiac really did offer a driver-operated exhaust cutout system that year, but not for very long.
Actually, remote-operated exhaust cutouts date back to the earliest years of the auto industry. Drivers could use them to operate their autos in town with a fully functional exhaust system, and then once out in the countryside they could open the cutout for greater performance, economy, and fun. Exhaust cutouts were standard factory equipment on the Duesenberg J and other luxury cars, but eventually they fell out of favor.
Courtesy of Bring A Trailer
Pontiac simply revived the concept with the Vacuum Operated Exhaust (VOE) option, officially designated RPO W-73 on the order form and priced at $63.19. A push-pull valve bolted under the dash (called a “Tiger Switch,” above) opened a manifold signal to a pair of vacuum servos, one on the front of each dual exhaust muffler (below). When actuated, the servos operated gates that allowed exhaust pressure to bypass the muffler chambers and increase the sound level. A check valvesin the vacuum line allowed the system to function at wide-open throttle.
Courtesy of Bring A Trailer
We can see that VOE was not really designed to minimize exhaust backpressure for maximum performance, but mainly to increase the noise level—the better to impress the other teenagers at the local drive-in. (There was no increase in rated horsepower.) Indeed, Pontiac produced a TV commercial for the 1970 GTO that showed the system being used for just that purpose, and you can watch it here. Pontiac’s tagline for the GTO that year was “The Humbler.”
This is where things get a little fuzzier. As the story goes, when the commercial was aired during Super Bowl IV, senior General Motors executives were horrified. The automakers were already under growing pressure from insurance companies and safety advocates about the muscle car menace, so the brass ordered the option killed instantly. However, it could also be noted that VOE potentially ran afoul of any number of state and local noise ordnances. But either way, the option was discontinued. Of the 40,157 GTOs produced in 1970, only 233 were equipped with the W-73 option. And as we know, a rare option in the muscle car world is often a valuable option.
Oh, what’s all the fuss? Loud things made a statement, it’s been said, you can tell when you are getting old, when loud things bother you. Funny how we pick and choose, for example, a Harley at 2am is annoying, however, the earsplitting noise of a top fuel dragster, or a Packard Merlin is music. Living in the rust belt, a loud exhaust was common. Any loud V8, beautiful, those fart can Subarus, oh please. You calls that an exhaust note? I never heard of this particular option, usually a cable or “manually opening up the headers” was common practice, but I think how this got to production is another matter entirely. I wonder if this was one of DeLoreans last ideas. Go out with a bang.
233 reached production. I wonder how many (if any) are still functioning today? As this was not a simple mechanical push-pull rod but depended on specific mufflers, and given the average lifespan of a muffler, plus the replacement parts were most likely never available, I’ll assume that there’s a few GTO’s out there with the W-73 switch proudly mounted but completely non-functional.
I remember seeing the TV commercial showing this.