At first thought, you’re probably wondering why anyone would put a catalytic converter on a classic musclecar, right? Well, don’t let the myths of the fuel crisis-era catalytic converters leave you too jaded on this forefront. Because if you really think hard about how far we’ve come with technology, you’d remember that some of the most potent musclecars today are making big power – with all of it passing through a pair of catalytic converters.

Along with their direct fit catalytic converters, Flowmaster is also offering universal catalytic converters to add to your exhaust system. Aside from the beneficial aspect of helping to clean up the environment, one dual-exhaust at a time, there are other benefits from these universal cats, as well, and this video above from Flowmaster shows one of those benefits.

The donor car is a 1965 Plymouth Belvedere II with an era-correct 318 Polysphere engine. But that’s where “stock” disappears and “custom” takes over, because the car has been modified. The 318 has been massaged a little, and produces close to 100 hp more at the crank than the original engine did, and on top of the intake is an EFI throttlebody conversion in place of the carburetor that once resided there.

The car was run on the dyno and put down a respectable 224.34 RWHP, not bad considering it’s a daily driver and occasional track car. But the benefits that came along with these 2.5-inch universal catalytic converters became evident when the car was run on the Dynojet dynamometer after the installation.

With the pair of high-flow cats added to the exhaust, we knew that there would be some additional back pressure, and that netted us a slight increase in RWHP, bringing us to 227.27 RWHP, for a gain of 3 horsepower. The torque remained the same, but the cats also act as a bit of a pre-silencer, too, and that makes those 70 mph cruises a little more bearable.

Is it typical that you’d see an increase in RWHP by adding high-flow catalytic converters? Probably not, and in some cases you might see a slight decrease, but either way the change isn’t something you will feel or notice. What is important is that you’re leaving slightly less of a footprint on the environment and these universal fit cats aren’t robbing valuable power from the engine – now that’s a win on both sides of the fence.

Check out Flowmaster’s universal and direct-fit catalytic converters on their website, and remember that these are 48-state converters, so be sure to check with Flowmaster and your state and local laws before to check for legality before you remove your old catalytic converters.