If you had to pick a single sound to represent the muscle car era of the late 1960s, it would be the guttural rumble of a well-tuned V-8 breathing through open exhaust pipes.
No other vehicle deployed the sound of throbbing bass notes with as much bravado as the 1970 Pontiac GTO, like the one recently for sale on eBay.
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Exhaust Cutouts
It’s a simple rule of automotive performance: to free up horsepower, allow exhaust gasses to flow as quickly as possible out of the engine.
Of course, engines producing thousands of explosions every minute can be deafening. That’s why cars meant for the street have mufflers - opens in new window or tab. that absorb much of that sound before the exhaust escapes the tailpipe.
However, mufflers create back pressure that can inhibit performance. So, enthusiasts started to remove them. When police clamped down on noise pollution, enterprising builders developed devices known as “exhaust cutouts - opens in new window or tab.” that could open the exhaust with a switch on the dashboard. That kept the car reasonably quiet until it reached the track.
Back in the day, Pontiac was tired of seeing the Mopar brands—Chrysler, Dodge, and Plymouth—rule the streets. After all, the GTO was arguably the first muscle car, dating back to 1964. So, the brand took the bold step of implementing an optional factory-fitted exhaust cutout for its 1970 model GTO. The option with a dashboard switch was known as a “vacuum-operated exhaust” or VOE.
Its Days Were Numbered
A Pontiac commercial - opens in new window or tab. for Super Bowl IV in January 1970 highlighted the VOE option package. In the ad, a driver cruising through a drive-in diner flicks a switch to rouse the crowd with a roar. The singing voice called this 1970 Pontiac GTO “The Humbler,” a reference to the effect the car would have on drivers challenging it to a stoplight drag race.
The VOE was option code W-73. But it took poring over the option book to special order the GTO with VOE. That difficulty with ordering the option makes the 1970 Pontiac GTO for sale on eBay incredibly rare. The seller says only 233 with the VOE option were produced before social and environmental factors killed the GTO with exhaust cutouts.
In the late 1960s, Americans became increasingly aware of vehicle emissions' environmental and health impacts. So, the government started mandating emissions control devices for new cars. Also, the 1973 oil embargo and the resulting gas shortages hurt the appeal for fuel-thirsty vehicles.
Safety was also becoming a more significant factor. Insurance companies started to charge high rates to muscle car owners after discovering that owners were disproportionately responsible for driving incidents.
A few weeks after the Super Bowl ad, General Motors pulled the plug on the VOE option. Risk-averse GM needed to maintain its good name—especially to regulators enforcing increasingly restrictive fuel and safety standards.
Showroom Fresh
The seller of this stunning 1970 Pontiac GTO did his research. He learned that only 35 GTOs with the W-73 exhaust cutouts were built with air conditioning and automatic transmission.
While we would never say no to a four-speed Muncie manual transmission - opens in new window or tab. in a car built for speed, the automatic in these cars makes daily driving easier. And the cold air provides comfort on hot summer days, especially after a long day in the sun at a car show.
Besides, take a look at the spotless trunk. There’s plenty of room for all the trophies its next owner will haul home.
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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.