Home » Ford’s Trick To Beat Emissions Regulations For The 1975 Ford T-Bird Was Both Genius And Stupid

Ford’s Trick To Beat Emissions Regulations For The 1975 Ford T-Bird Was Both Genius And Stupid

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Today, emissions standards are both well-defined and strictly enforced. Cut back to the 1970s, though, and restricting automotive emissions was still a new art that automakers were getting to grips with. That led to all kinds of inventive solutions, and a particularly cheeky one from Ford.

The story comes to us from Rare Classic Cars and Automotive History, a YouTube channel which covers the car stories of yesteryear. A new video covers the oddball solution Ford found to meet 1975’s emission standards on a budget.

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As covered by the New York Times in 1975, Ford had just decided to roll out catalytic converters across all its models. Its big full-sized vehicles with V8 engines all got dual catalytic converters, just like today’s vehicles. However, for the 1975 Ford Thunderbird and Lincoln Continental Mark IV, the Michigan automaker found a sneaky little workaround.

Why Not Just One?

There were two main solutions for putting cats on big V8 vehicles in this era. GM decided it could go with just one big pancake-shaped unit. It combined the exhaust headers from both banks of the engine into a single pipe which fed a single big catalytic converter. Ford, on the other hand, used a more modern solution on the LTD, Grand Marquis, and the Lincoln Town car. Each bank of cylinders had its own cat up near the headers. This made perfect sense for cars with dual exhausts.


Of course, this was expensive, as it required Ford to fit two cats, which didn’t come cheap. The 1975 Ford Thunderbird and the Lincoln Continental Mark IV would make do with one cat instead, a decision that surely saved a lot of money. However, the cheeky part was this. Ford only attached it to the driver’s side cylinder bank. The passenger-side bank simply went without one!

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Note the large bulbous catalytic converter on the driver’s side exhaust, and the total lack of cat on the passenger side. 
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This is actually how these cars came from the factory – one bank of cylinders vented its exhaust entirely untreated!

If you’re familiar with modern cars, you’ll be used to seeing dual cats on cars with V-engines and dual exhausts. The entire exhaust stream needs to pass through a catalytic converter in order to pass modern emissions. Apparently, though, that wasn’t the case in 1975. Ford was able to skate by with these models, still meeting emissions standards while only running half of the exhaust output through a catalytic converter!

Notably, there was an H-pipe that connected both sides of the exhaust. However, this was after the cat, not before. Thus, the exhaust from an entire bank of cylinders was largely going entirely untreated by the cat.Cabpi

GM used to feed both cylinder banks into a single catalytic converter. It worked.

This choice had some pros and cons. On the one hand, it saved Ford quite a bit of money. Catalytic converters have never been cheap, so using one instead of two is naturally much more cost-effective. On the other hand, though, the cars still suffered one major drawback. They still needed unleaded petrol to avoid poisoning the single existing catalytic converter.

Ultimately, you’d never get away with this today. Modern emissions standards wouldn’t even let you run a single cylinder of an engine without passing it through a cat. Emissions of carbon monoxide and nitrous oxides from an untreated exhaust stream are simply too high. But back in 1975, you could skate by just cleaning up half the output from a V8.

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Compare with this modern Mustang exhaust system from Flexx Motorsport. Note how each bank of cylinders feeds through its own catalytic converter before the H pipe.

It truly was a different era back then. Today, we’re blessed with cleaner-running vehicles and nicer air as a result. Still, it’s amusing to see what Ford was willing to try to get by in the bad ol’ days of the 1970s.

Image credits: Rare Classic Cars & Automotive History via YouTube screenshot

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16 hours ago

This is hilarious…that reminds me, I still want a 79 Lincoln Mark V (of course w/ a nice modern exhaust!)
So did they also do this w/ DT’s “cat” Jeep?! I’ll see myself out…

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