Abandoned History: Cadillac’s Northstar V8, Head Bolts and Gaskets Aplenty (Part II)


abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

We return to Abandoned History’s coverage of the Cadillac Northstar engine this week, at a pivotal moment in the engine’s development. Stiff competition from luxury cars of domestic, European, and Japanese origin put big pressure on Cadillac. The era of the dual overhead cam engine was on the horizon, and it looked as though Cadillac was about to be left in the dust with its High Technology 4.5-liter. After hemming and hawing about an update to the 4.5 rather than the development of a new engine, GM brass decided a new power plant was in fact necessary. However, aside from the necessity of DOHC technology, the rest of the engine was just a word cloud of ideas that needed to be nailed down quickly.

Perhaps the most basic early decision to make was the engine’s displacement. Cadillac had long used the Chevrolet 305 (5.0L) and 350 (5.7L) V8s, and Corvette’s upcoming LT5 was also 5.7 liters. Competition from Japan would use 4.0- and 4.5-liter V8s. Mercedes and BMW used V8s with displacement of between 3.0 and 5.5 liters.

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

Cadillac desired power that was enough but not too much. Engineers also had to consider the sort of cars the brand would make at the turn of the Nineties. Historical events and product planning decisions conspired to catch Cadillac out in the Eighties and into the early Nineties. 

As previously mentioned, circa 1985 the brand wanted to shed its “old people only” image, and chase the younger and affluent European car buyer. That was combined with an ill-timed secondary round of downsizing and a switch to more efficient front-wheel drive platforms (except Brougham). The Northstar V8 would lie in a transverse layout and power these front-wheel drive cars in a luxury car world where every single competitor used rear-wheel drive. 

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

Those considerations in mind, the displacement range was narrowed to between 4.0 and 5.0 reasonable liters. This range was also fully within the specs for the current crop of Cadillac models, which began in the HT4100 era and easily adapted to the 4.5. The preliminary displacement target ended up being 4.5 liters for the Northstar. Further development considerations eventually pushed that up slightly to the production 4.6 liters. 

At this point the other side of the development team began conducting focus groups and clinics with potential customers, to see what they might want from an all-new Cadillac engine. Unfortunately, the folks who put together the group’s attendance list made a mistake: They filled the sessions with “prospective” Cadillac customers, but many of those already had a Cadillac in their garage. Inviting brand loyalists to ask them what they might want in the future can lead to an echo chamber effect. 

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

It was an interesting decision, and one which was not given enough consideration. Separating the potential customer groups into owners and non-owners may have been more productive. As it turned out, the list of characteristics desired of the new engine was nothing surprising. 

The focus groups put reliability high on their list, as well as precision engineering, and controlling the weight and size of the engine. Value was also on the list, as well as overall efficiency. The groups also wanted the engine to be easily serviceable, and to feature the latest in technological innovation. Notice what’s lacking from the list?

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

Performance. Because of the group makeup, there was no emphasis or ask for performance. Consider how the competition treated the importance of V8 performance in its product of the era, and inversely how the typical Cadillac owner of the Eighties would not have worried about such a thing. One can almost picture the old guy sitting in the focus group in 1987, thinking how he’d like to buy another boaty Coupe DeVille soon. 

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

After the magical list of requirements and displacement was passed to engineers, design of the engine began in earnest. A 90-degree layout was chosen, along with an aluminum engine block for lightness. The block was separated into two pieces, with its separation at the center of the crankshaft. 

The Northstar had a couple of unique features in its design, one of which was an oil distribution plate attached to the lower crankcase. The plate used channels which aligned to channels and holes on the crankcase and sent oil to the oil pump and crankshaft. The implementation of this plate meant there was no need for drilled oil passages in the cylinder block. 

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

Northstar used an open deck design (unlike cast iron V8s). It also used iron cylinder liners, which were designed with an eye to suitability during extended high operating temperatures. The engineering team took extra time to consider the different thermal expansion properties of aluminum engines that used iron crankshafts. They also determined that an alloy of aluminum-lead was the solution for the main bearings. 

Mating the cast aluminum block with the cast-in-place iron cylinder liners proved difficult, and slowed the engine’s development. Additional time was taken to refine manufacturing of the aluminum block dies. Additionally, engineers performed computer modeling of materials solidification to ensure the block was strong and would last. 

abandoned history cadillac s northstar v8 head bolts and gaskets aplenty part ii

Development of the first-ever Cadillac engine with dual overhead cams was a rigorous process. The design was intended to make the best use of the four-valve layout for the optimal air and fuel mixture, to ensure lower emissions and high power figures. Spark plugs were offset 1.5 millimeters toward the exhaust side of the combustion chamber to improve efficiency.

The Northstar was coming together, but Cadillac continued to make mistakes with regard to materials and engineering choices. In our next episode we’ll cover the difficult birth and execution of a magnesium induction system which would last for a single production year. We’ll also review Northstar’s unique cooling system that made big news upon introduction.

[Images: GM]

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