The $35,000 Hot Hatch question

[FoMoJo]

Well, it's the same reason why an motor is replaced - it was old.

The FE dates back to the '50s, and was the contemporary of the first gen Hemi and Chevy W block. By the time '65 rolled around, Mopar moved onto the second gen 426 Hemi and the later iterations of the RB motor (383/440), and Chevy debuted the Mark IV big block. Ford saw the light at the end of the tunnel - the FE could not compete with these motors, especially if the horsepower wars were to continue.

Enter the 385 series debuting in 1968 - beefier block, longer rods, bigger values, better head design (canted valves), larger crank/rod bearings. As we know now, not long after the 385 was introduced the muscle car era was over, and performance versions of the 385 - Boss 429, 429 CJ, 429 SCJ - never quite got off the ground, and the FE lived on well into the '70s.

Certainly, engine design evolves, however, in many ways the FE was far ahead of its contemporaries well into the 60s and even the 70s...The FE's thinwall casting production method was innovative and forward-looking in the mid-1950, resulting in lower weight and dramatically reduced production costs. Ford's competitors at the time required thicker castings to mask the flaws and defects that resulted from their processes. Improving quality and allowing thinner walls was accomplished through many engineering improvements, including reducing the number of cores required to cast an engine block. Fewer cores made it easier to assemble the overall mold for casting and reduced the number of potential problems.[48] In the late 1980s when both Ford and GM revamped their V8 offerings, many of the FE's designs and engineering were incorporated in the new engines, including the deep skirt, cross-bolting of the mains and thinwall casting.

It should also be mentioned that for the FE series, and even the Y-block preceding the FE, a higher content of nickel was used for additional strength; though the Pontiac division of GM also used more nickel in their versions of the small block...it was better than Chevy's small block.

It should also be noted that the FE 427 was developed as a racing engine and with the SOHC version, outperformed everything else at the time, including the 429 "Boss" engine.  Very much ahead of its contemporaries.

Also, the 428 CJ and SCJ engines, a cobbled version of the FE 406 bore and FE 410 stroke, was a torque monster beating everything in class on the strip in the late '60s including the revamped Hemis and GM's latest offerings. 

However, as mentioned previously, the thin-wall casting limited the displacement; 428 was the maximum CI achievable, therefore, as its competitors were going 'big', it was necessary for Ford to come out with a true big block, hence, the "385" series; incorporating a number of innovations pioneered by the FE series.

[GoCougs]

These days there are plenty of FE stroker kits available up to 500 cubic inches, so the 428 limit doesn't hold, but that's moot of course, since all performance variations of the 385 were 429 cubic inches.

Ford knew what it was doing - the FE couldn't go head-to-head with the new competition - just too old - ergo, Ford spent a lot of time and money to replace it.

[FoMoJo]

Of course you can stroke it up to about 484 CI with maximum stroke, but the bore was the limitation due to the thin wall design.  The 427 had a maximum bore at 4.232" with a possible overbore of .030", after which you would be in the water jackets.  The Mopar block could go up to 4.50", 4.625" at a pinch, and could be configured to over 600 CI with maximum stroke. Bear in mind that the 427 was not a production line engine; it received specialized precision grinding treatment at Ford's speed shop and it's purpose was track racing, NASCAR and ultimately Le Mans.  Stroked engines were for the drag strip.  You benefited from increased torque, the 428 CI was an excellent example of this, but you lost out on revs and bhp.

The factory bore of the 385 series was 4.36" with options for overbore.  The stroke on the 429 was 3.59" and for the 460 was 3.85", hence the series name.  Lots of room for increased displacement.  Of course lessons learned from the FE series were incorporated along with improved head design for better flow; but nothing quite matching the FE 427 SOHC with straight ports from the intake and out to the exhaust.