American carmakers in the 1960s chased trends like Metallica cutting their hair. Seemingly, every brand had to have a large displacement V8, even producing consecutive 425, 426, 427, 428, 429, and 430-cubic inch engines. Sometimes, different manufacturers offered identically sized V8s, such as the Pontiac, Oldsmobile, and Buick 455s.

Now, advertised displacements weren't always accurate. For example, the Ford 427's 4.232-inch bore and 3.784-inch stroke results in 425.82 inches of displacement. When the 427 FE debuted in 1963, NASCAR had a 427-cubic inch limit, so Ford apparently just called its 426 a "427" to match (or to avoid mirroring the Chrysler 426 Hemi). Chevrolet's 427 actually is a 427, though, with its 4.25-inch bore and 3.76-inch stroke yielding 426.72 cubic inches. 

So, bore and stroke are darn similar between the Ford and Chevy 427s, and output figures were often nearly identical, too. R-Code Ford 427s made 425 horsepower at 6,000 rpm and 480 pound-feet of torque at 3,700 rpm. Chevrolet L72 427s made 425 hp at 5,600 rpm and 460 pound-feet of torque at 4,000 rpm, though early 1966 L72s carried a rating of 450 hp. 

Chevrolet's 427 enjoyed a wide spread of performance tuning, from sedate 10.25:1 compression 335-hp LS1s  (completely unrelated to the C5 Corvette gen-III small block LS1 from the 90s) to wild, solid-lifter, 12.5:1 compression competition-oriented L88s with a factory-rated 430 hp (more like 550+). In comparison, Ford didn't build 427s for relaxed cruising. The only sub-400-hp 427 FE was in the 390-hp 1968 Mercury Cougar GT-E. Ford's 427 was an expensive, high-strung engine, while the cheaper-to-build 428 FE was better suited for the street, prioritizing torque over revs, due to its smaller bore and longer stroke.

Both Ford and Chevy experimented with exotic specs on their 427s, but in opposite directions. In 1964, Ford slapped single overhead-cam (SOHC) heads on the 427 FE. It wasn't really that simple, of course, though the engineering process was so fast that the SOHC 427 is nicknamed the "90-day wonder." A 6-foot long double link roller timing chain spins both camshafts in the same direction, meaning the cam lobes on one bank rotate toward the intake follower while the other cam does the opposite. The solution was to use camshafts that were mirrors of each other. Sodium-filled exhaust valves and stainless steel intake valves take care of airflow in the hemispherical combustion chambers. 

The 427 "cammer" thundered 650+ horsepower with dual four-barrel carbs. NASCAR passed hard on the outlandish engine at first, but was willing to relent if Ford would simply add 430 pounds of penalty weight to its cars. Ford turned down the deal and sold the engines to drag racers like Don "The Snake" Prudhomme. If that name's unfamiliar, getPrudhomme's awesome book, "My Life Beyond The 1320."

Meanwhile, Chevrolet engineers were more interested in weight. Those mad scientists wanted small block weight from a big block 427, so out went the cast iron engine block, and in went aluminum. Thus, the 520-pound 1969 ZL-1 427 was born. ZL-1s dropped to 12:1 compression, but their open chamber, larger-port heads breathed better. The aluminum monster made it into 71 cars from the factory (69 Camaros and two Corvettes), and, even then, they were only possible thanks to central office production orders (COPO) from dealers like Fred Gibb Chevrolet.

Here's a twist ending out of an Agatha Christie murder mystery. One of these engines secretly isn't a big block. The Ford 427 FE is actually a "medium block!" Ford did make big blocks – the 385-series, which gave us the 429 Cobra Jet, Boss 429, and 460 V8s. The 385-series' 4.9-inch bore center spacing is extremely wide. Ford's FE V8s have a respectable 4.63-inch bore spacing, which is still plenty for the 400+ cube displacements Ford gave them, but the 385-series is where the truly atmosphere-gulping V8s spawned from.

Chevy's big block 4.84-inch bore center spacing is nearly as large as Ford's 385-series, and it certainly dwarfs the FE. It's that bore spacing that's most responsible forChevrolet's ability to offer new 632 big blocks that avoid paper-thin cylinder walls. This larger bore spacing is also why 428 cubic inches was the end of the road for the FE, as Ford began gravitating more toward the bulkier 385-series, while Chevrolet continued punching out its big block to ever larger displacements.

In 1970, Chevy dropped a 454 bomb, offering up to 450 hp and 500 pound-feet of torque (yes, these are gross ratings) in the LS6. Even as Chevy big blocks got more asthmatic with smog controls, GM still upped displacement to 496 cubic inches for the8.1-liter Vortec that was the last of Chevy's big block era.

Finally, and more generally, Ford and Chevy engine designers evidently had spectacularly different mindsets on interchangeability and consistency. Switching parts between different Chevy V8s is usually trivial. Heck, even big blocks and Gen-I and II small blocks use the same firing order. But try swapping parts between Ford Cleveland and Windsor 351s, we dare you.