In an earlier story at Mac’s Motor City Garage, we told of an experimental Cadillac V12 from the 1960s that never made it into production. Here’s another Caddy V12 that found a similar dead end—this one only a few years ago. 

 

Cadillac’s first and only production V12 was originally offered from 1930 to 1937. Known internally at Cadillac as the 370 series, this 368 CID engine (below) was closely based on the architecture of the Series 452 V16, including its 45-degree bank angle. The narrow vee angle was less than optimum for a V12, but with six firing impulses per crank rotation, it was still extremely smooth.

With a bore of 3.125 inches and a stroke of 4 inches, the V12 was ultimately rated at 135 hp, compared to 165 hp for the regal V16. Only a few thousand of the magnificent V12 and V16 Cadillacs were produced in the classic era, but they generated a mystique for the Cadillac brand that General Motors has dreamed of recapturing ever since.

 

1931 Cadillac 370 V12 

 

The most recent Cadillac V12 to officially see the light of day was unveiled at the 2002 North American Auto Show in Detroit as the powerplant in the Cadillac Cien concept. A 7.5L, 60-degree  variant of the Northstar 90-degree V8, more or less, the Northstar XV12 (official name) was rated at 750 hp—which is an ambitious 100 hp per liter.

Advanced features added to the DOHC, four-valve Northstar’s architecture in the V12 version included GDI (gasoline direct injection), displacement on demand, and a carbon fiber, three-phase tuned intake manifold with twin throttle bodies. But by 2009, Cadillac’s Northstar engine family had run its course. Complicated and costly to build, the Northstar was demonstrably inferior in several ways to GM’s LS V8, a more simple yet highly effective pushrod design.

Meanwhile, the flagship DT7 sedan project, the ideal platform for a premium multicylinder engine, was torpedoed by GM’s collapse and bankruptcy. Once again, Cadillac’s V12 ambitions were dashed. (Note: There’s an interesting followup to one of the photos in this feature you can check out here.)

 

2002 Cadillac Cien Concept 

 

Cadillac recently revived its plans for a flagship vehicle, now based on the GM Omega platform, but the engineering focus this time around, we can presume, is on green technology including diesels, plug-in hybrids, and turbocharged fours and V6s.

For more than 50 years, Cadillac division has been experimenting with a diverse array of V10, V12, and V16 prototype engines, hoping to revisit the multicylinder magic of the classic era. Are these plans now officially dead and buried?  We’ll see. In the meantime, here are some detail photos of the Northstar V12 that would never be.

 

Cadillac XV12 concept engine

 

Cadillac XV12 displacement on demand 

 

Cadillac XV12 GDI manifold 

 

Cadillac XV12 front view 

 

Cadillac Cien and Cadillac LMP racer