Today's horses must be Clydesdale-class, at least when compared to the horses we were saddling up back in the 1960s and early '70s. How else can you explain the real-world performance figures of yesteryear, when muscle cars were routinely pushing out well over 400 horsepower and quarter-mile timeslips in the 14s, with the 12-second runs we see today from a similar number of (rated) ponies? Well, actually, there are a number of reasons... and none of them has anything to do with a four-legged horse or the way we calculate how much power that animal may have (that's another sordid affair for another sorted time).
For one thing, there's the issue of the actual rating process. Before 1971, engines were factory rated using a process defined by the Society of Automotive Engineers as 'Gross' horsepower. This figure was calculated on a test stand with no intake, exhaust or power-robbing accessories attached. After 1971, power levels dropped as manufacturers re-rated engines using the SAE's 'Net' process, which added intake and exhaust restrictions and the load of engine accessories, like the alternator and power-steering pump.
But there must be an equalizer, right? How do we know how much horsepower our favorite classic muscle cars really put down as compared to our latest batch of favorites from today's showrooms? We suggest you check out this informative article from Hagerty, which explains why a horse is a horse, of course, and why we shouldn't necessarily take off our rose-colored glasses even when presented with clear-as-day performance numbers that show things are better today than they had ever been in the past.