Muscle Cars Were Slow… II

About two weeks ago, I got a new (2016) Mustang GT to test drive. 435 hp. This is a mass-produced, docile, AC-equipped street car with a dead-calm idle. Anything from back in the day – the ’60s and ’70s – that made that kind of power would have been a handful to drive on the street and also would almost certainly have been either a low-production, bracket race-intended animal (e.g., an L88 427 Corvette) or modified.

Almost nothing that came from the factory back in the day made 435 hp.

Or even 335 honest hp.

I wrote about this before (here) and there was much wailing and gnashing of teeth. It does not alter the truth. Hindsight is not 20-20. Most of the first-generation muscle cars were weak… by modern standards.

The turbo four cylinder (315 hp) version of the current Mustang is probably about “par” for what was available from the factory in a typical V8 muscle car from the late ’60s/early ’70s, in terms of horsepower and performance. The current EcoBoost Mustang’s output, if calculated using the SAE “gross” method that was used up until 1972, would likely be right around 360-380 hp, in the same ballpark as (for example) a ’70 Camaro Z28 LT-1 or a 440 four barrel ’71 Plymouth GTX.

Only a small handful of elite classic-era muscle cars touted more gross hp than that.

The famous Chrysler 426 Street Hemi with twin four barrel carbs was one of the very few – and its advertised 426 hp was close to as good as it got.

And nowhere near what something like a new Dodge Challenger Hellcat (article here) offers (707 hp).

And when SAE “gross” horsepower ratings changed to SAE “net” ratings – the engine in production tune, installed in the car, with a full production exhaust… as opposed to on an engine stand, with open headers and tuned for maximum output – even the strongest of the classic-era muscle car’s numbers wilted.

But it was a much more honest measure of an engine’s true output.

For example, one of the strongest factory-stock classic-era muscle cars was the 1973-’74 Super Duty 455 equipped Pontiac Trans-Am and Firebird Formula. These were pretty much the quickest factory stock cars Pontiac sold up to that time. The SD-455 TAs and Firebirds were quicker through the quarter-mile (low-mid 13s) than all but a handful of the most feral late ’60s stuff, such as the L-88 Corvette already mentioned and others like it (of which there were very few).

The SD-455 was a special engine, very low production and assembled on a separate line. It shared only its displacement with the more common (and non-SD) 455 V8s used in other Pontiacs (including run-of-the-mill Trans-Ams). It had a special heavy-duty block, specific high-flow round port cylinder heads based on the race-only Ram Aim IV heads Pontiac designed for the Trans-Am race series, an aggressive camshaft, big four barrel carb and a bunch of other special equipment, including provisions for dry sump oiling. Yet this huge – and radical – engine – produced how much power?

290, SAE net.

Less than the current Mustang’s four cylinder turbo engine. And not even half what the new Hellcat’s engine delivers.

Now, there is a qualifier.

The old stuff seems fiercer. Feels quicker. Sounds tougher.

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