Video: Promotional Video For Cadillac’s Doomed HT-4100 Engine

In 1982, Cadillac needed a new engine for its new lineup of luxury cars, and GM had the answer in the form of the HT-4100. The problem was that Cadillac buyers didn’t just want power and performance anymore; they demanded low-emissions, high-MPG cars. That meant a lightweight V8, and GM thought it had the solution with an aluminum engine block. It was a good idea, one that many automakers are utilizing today.

The problem was that GM decided to top the engine off with iron cylinder heads and inferior internals that led the HT-4100 to become something of a running joke among engine enthusiasts. Often decried as one of the worst engines ever made, we thought it would be funny to take a gander at a promotional video for the HT-4100 put up by our friends over at

The “HT” in HT-4100 stood for “high-technology”, and the 4100 referred to the 4.1 liters of displacement. This light-weight, bi-metal motor utilized a computer-controlled throttle body injection, a high operating temperature to reduce emissions, and replaceable cylinder sleeves that were supposed to improve engine longevity.

Unfortunately the HT-4100 was prone to a lot of problems, chief among them intake gasket failure due to “scrubbing” between the bi-metal surface. The aluminum oil pump was also prone to failure, and the aluminum thread bolts were often stripped as the bolts peeled loose. Even though GM sold over 100,000 cars equipped with the HT-4100, it is universally maligned for some clever designs executed in the worst way possible.

GM has made its fair share of bad engines; can you think of anything worse than the HT-4100?

About the author

Chris Demorro

Christopher DeMorro is a freelance writer and journalist from Connecticut with two passions in life; writing and anything with an engine.
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