Seemingly poised to order more Superpower T-1s, Norfolk & Western's success with their home-built Class A 2-6-6-4 prompted the C&O and Lima to consider a more modern articulated design.

Utilizing the 6-wheel trailing truck design permitted the firebox of the locomotive to be longer and deeper, promoting enhanced coal combustion.

During test runs, the class was shown to exert up to 119,500 lbs of starting tractive effort with drivers worn to 65.5 in (1,660 mm) inches.

Peak horsepower output occurred between 40 and 50 mph (64 and 80 km/h), with dynamometer car readings ranging from 6,500 to 7,500 hp (4.8 to 5.6 MW).

The locomotives sported the latest developments in steam technology, and came equipped with front-end multiple valve throttles, type E superheaters, schedule 8-ET brakes, low water alarms, continuous blowdown, automatic lubricators, roller bearings on all axles, etc.

[5][6] This unusually high weight led to adhesion factors exceeding 4.5, which meant that the locomotives had a good grip on the rails and were unlikely to slip in regular service.

To ensure the locomotive would fit on the largest turntables on the C&O, but still carry enough fuel and water to make division points on the railroad, the tenders were made as short and as tall as possible.

Returning west from Clifton Forge, the ruling grade was 1.14% and the H-8s were rated for 2,950 tons of empty coal hoppers and manifest freight unassisted.

[1] The H-8s also handled coal trains and time freights from West Virginia to Columbus and Toledo, Ohio alongside the older T-1s.

Here, the ruling grade was a slightly stiffer, but much shorter one-and-a-quarter mile of 0.7% trackage west through Limeville, Kentucky leading up to the bridge over the Ohio River, and the H-8s were rated for 13,500 tons (160-cars) unassisted.

Were it not for this 160-car limit, the H-8s could have easily handled trains approaching 200 cars and 17,000 tons unassisted over this division, save for the helper districts at Limeville, KY and on the 15-mile, up-to-0.5% grade of Powell Hill just north of Columbus, OH.

1642 suffered a crown sheet failure and subsequent boiler explosion due to a prolonged low water condition at Hinton, WV.