While the High Technology engine was being developed, due to higher Corporate Average Fuel Economy standards being phased in by the United States government, Cadillac introduced a variant of their traditional V8 engine with the first usage of cylinder deactivation for 1981 as a stopgap measure to increase the fuel economy of their lineup.

GM released EPROM updates hoping to increase drivability and reliability, but could not overcome the primitive state of engine control technologies at the time, and the V8-6-4 was discontinued for 1982, with many owners disconnecting the cylinder deactivation system.

A new line of downsized Cadillacs with the transverse mounted V8 engine and front wheel-drive was slated for launch in 1983, however, delays in the downsizing program shared with Buick and Oldsmobile postponed their debut until mid 1984 when they were introduced as early 1985 models and shared what is known as the "Metric" bellhousing pattern.

The HT4100 also adopted other modern design features including replaceable cylinder sleeves, high operating temperature for emission control (210 degrees, compared to 180 in earlier engines), free circulation of coolant between the block and the heads, and bimetal construction that mounted heat-tolerant cast-iron heads onto a weight-saving aluminum block.

The Allanté 4.1 had a new, reinforced engine block that would later be used in the Cadillac 4.5, it used a different camshaft profile and roller lifters to provide for improved airflow, in addition to multiport fuel injection.

Other than the basic architecture, the only thing the Allanté 4.1 shared with the HT4100 was the displacement, something easily changed in the engine family by simply using different diameter cast-iron cylinder liners.

A bored-out (to 92 mm (3.62 in)) 4.5 L (273 cu in) 4.5 version was rated 155 hp (116 kW) and featured throttle body fuel injection.

Despite the fact that it had similar output to the Allanté's 4.5 L port fuel-injected V8, the 4.9 L engine represented a significant upgrade for the remainder of the Cadillac lineup.