Why the Cadillac V8-6-4 Was the Worst Engine of the 1980s?

The name Cadillac V8 can refer to any of the many V8 engines built by the Cadillac Division. Production of these engines began in 1914 when General Motors’ Cadillac Division released the first mass-produced engine.


Most Cadillac V8s were good, but in 1981 Cadillac introduced a new engine that would be known for its complex electronics, the V8-6-4 (L62).

GM was betting on something significantly ahead of its time. As a result, it was a complete catastrophe. The reason it failed was that the technology wasn’t sophisticated enough for the job.

Cadillac made the V8-6-4 because gas prices got more expensive. So GM came up with methods to deactivate cylinders. The methods allowed V-8 engines to cruise on four cylinders occasionally and save a few miles per gallon.

All Cadillac models in 1981 came with the V8-6-4. This infuriated the public even more because there was no other engine option. Critics argued that Cadillac’s engineering team thought beyond technological limits without respecting those technological limits.

Let’s see what made the V8-6-4 a disaster and why the public hated it.

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Here’s How the V8-6-4 Works

Cadillac V8-6-4 engine side view
Via: Bring A Trailer

The first time cylinder deactivation came to light was in 1905, with the Sturtevant 38/45hp. A more fuel-efficient cruise could stop three of its cylinders. In 1917, the Enger Twin-Unit Twelve used this method. This Cincinnati-built machine had an owner-operated cylinder shut-off, activated by a lever on the steering column.

General Motors didn’t use the method until Cadillac tried it in 1981. The Cadillac L62 V8 was standard in every model it made for the 1981 model year, except the Cadillac Seville. GM’s engineers brought in the Eaton Corporation, an electronics supplier, to come up with a way to disable cylinders on demand.

They created a throttle body dependent fuel management system intended to shut down two or four cylinders, depending on the load. This would help the V8-6-4 claim a 30% fuel saving over previous powertrains.

The system achieved this by combining a microprocessor with an array of sensors that monitored everything in the engine. It monitored intake manifold pressure, engine speed, and coolant temperature.

When the system determined that the car was cruising and acceleration requirements were minimal, it activated a solenoid that mechanically locked the rocker arms, preventing the camshaft from operating the valves in certain cylinders.

Any misfires that ended up in the passenger compartment had to be absorbed by compressed air in the cylinders.

The reason why the V8-6-4 didn’t work

Cadillac V8-6-4 engine front view
Via: Bring A Trailer

The Eaton-GM partnership had grossly underestimated the computing power needed to spout the sensor readings coming out of the L62 when used in the real world.

Whether the car was accelerating or braking, the rocker control system was not fast enough to respond to the driver’s right foot. This problem caused delays in power production, which prevented the motor from running smoothly.

The fuel injection and deactivation systems had crossed wires to the point that neither understood what condition the engine was in. This meant that the throttle body poured either too much or too little gasoline into the engine, depending on how many cylinders were actually in it. operation.

At certain cruising speeds, the processor would get so excited that it would rush between cylinder counts, rocking back and forth like an automatic transmission that couldn’t quite find the right gear for the scenario.

The Cadillac V8-6-4 came with a gauge on the dash called the MPG Sentinel that would indicate how many cylinders were pulling at the time. The sentry proved to be useless, as the near-constant reluctance and lurching in the deactivation process immediately warned the drivers how many pots were being fired.

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The V8-6-4 wasn’t the only bad engine Cadillac made

Cadillac 4100 V8 engine in Eldorado
mr. choppers via wikimedia

After the introduction of the infamous V8-6-4, GM desperately wanted to get out of embarrassment. They introduced the HT4100 V8. The HT stood for ‘High Technology’ and the displacement was 4100 CCs (cubic centimeters) or 4.1 liters to use the more conventional measure.

Since it featured a fuel-injection system with throttle body and a lightweight aluminum block with cast iron sleeves, the HT4100 V8 seemed like a game-changer.

It was part of the Cadillac range from 1982 to 1987. It initially received positive feedback for its seamless operation. But the engine was slow. The HT4100 V8 had 125 horsepower and 257 pound-feet of torque, making it about as powerful as a V6. Couple that with the weight of a Cadillac and you can see why it couldn’t get out of the way.

Furthermore, the HT4100 V8 was plagued with complaints. It had head gasket issues, coolant leaks and oil pump failures. Replacement parts were prohibitively expensive and most repair shops refused to touch them.

General Motors suffered another engine failure. This prompted GM enthusiasts to go for the 4.1-liter Buick V6 available in select Cadillacs. It wasn’t as advanced as the HT4100 V8, but it was significantly more reliable and hassle-free.

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