Cadillac offered the disastrous V8-6-4 for only one model year, but the engine left a big, fat black mark on the permanent record of GM’s proud luxury brand.
On today’s cars, cylinder deactivation systems are commonplace. Marketed under various trade names including Active Fuel Management and Modulated Displacement, these setups deactivate the engine’s cylinders under reduced loads to improve fuel economy. And they work great, too. They reduce fuel consumption significantly, while the driver and passengers can barely detect them in operation. But that was certainly not the case when the General Motors Cadillac division tried an early version of the technology in 1981, labeled as the V8-6-4. Nothing short of a disaster for Cadillac, the V8-6-4 was discontinued after just one model year.
Formally known as the L62 V8, the V8-6-4 was essentially Cadillac’s 368 cubic-inch V8 (6.0 liters) with some key additions: Mainly, a set of electronic solenoids atop the number 3,4,5, and 6 cylinders that could deactivate the rocker arms on those respective cylinders as commanded by the engine’s electronic control module (ECM, or in Cadillac lingo, CCM). Tall rocker covers housed the solenoids and associated hardware, as shown above. For 1981, the L62 V8 was standard equipment on all gasoline-powered Cadillacs.
As the system tracked engine speed, road speed, engine load, and a host of other factors, the module could cancel out two cylinders, creating in effect a 4.5-liter V6, or cancel four cylinders to replicate a 3.0-liter V4. The system, developed by the Eaton Corporation, major supplier to the automakers, promised the best of both worlds: a powerful V8 for acceleration, and a thrifty V6 or V4 for economical cruising. In theory, anyway.
By pushing a button on the instrument panel, the driver could watch the V8-6-4 system in operation via the MPG Sentinel, a digital display that also reported the estimated fuel consumption (white circle below). But in practice, the driver didn’t need a display to tell him the system was working. It was all too obvious from all the bucking, shaking, and other symptoms generated by the apparatus.
What went wrong? To make a rather long story short: GM’s early throttle-body electronic fuel injection technology wasn’t fast enough, nor sophisticated enough, to deliver seamless operation. And the electro-mechanical solenoid setup that manipulated the rocker arms wasn’t up to to sufficient speed, either. Four-cylinder performance was as horrible as you imagine, while the system would also hunt around among the 4,6, and 8 cylinder modes at steady road speeds, among other problems. The technology required to perform cylinder deactivation properly wouldn’t be ready for prime time for another decade or more.
After more than a dozen attempts to revise the system, Cadillac discontinued the feature at the end of the 1981 model year and advised its dealers to disable it for the customers who were having problems. The V8-6-4 was a memorable failure in the history of Cadillac V8s, but unfortunately, it wouldn’t be the last.
You could do a whole series on Caddy engine disasters: 4100 V8, 5.7 diesel, Northstar…
We had a ’97 Cadillac Sedan DeVille which had the Northstar engine. We were quite satisfied with it’s performance. Mileage was very decent and power was outstanding for an automobile of that size and weight.
I had great experience with two Northstar Cadillacs, but they were meticulously cared for and maybe I was lucky. I know the failure rates ran high.
All the electronic nannys on cars these days make the cars throwaway. They cost more to fix than the car is worth.
Euro cars seem to be the worst but none are very good,, are are very good for manufacturers and dealerships.
I agree with you. Why do we need a computer to adjust the AC and heat for us? Have we really became that soft? Simple manual controls worked for years without failures, now, a single sensor failure can be thousands of dollars. No wonder you never see 80’s and 90’s vehicles on the roads anymore, their electronics became outdated and repair parts became impossible to find, so they got junked. A throwaway society indeed.