It never made sense to me either. It may have been to give each division it's own distinct flavor or part of GM's bid to not fall victim to the Sherman Anti-Trust Act. GM is, to steal from Winston Churchill, "...a riddle, wrapped in a mystery, inside an enigma". Of course he was speaking of the Soviet Union, but I think it fits here too.
GM is not Toyota. It has it's own corporate culture that has nothing to do with logic or efficiency. It is so top heavy with bureaucracy that any changes that need to be made take so long that it can never adapt to the market. Couple that with the UAW's unwillingness to adjust to market conditions and you have a recipe for disaster. The SBC is a good engine in many ways, but why, oh why was it used in production models for 45 years? The only car companies that moved slower were the British-and we see what happened to them. They produced the same exact car for 41 years-the Mini- with the same engine-BMC A series- and it was an even older design than the SBC! ( It dated to the Morris Minor of 1952)
An unwillingness to adapt to new market needs and build well-engineered products kills companies. GM it seems adds new features and technologies to check off a box on a list of components with little though as to how well they actually work. GM Diesels are one example, the original Corvette IRS is another. The original Corvette IRS had awful geometry but was used as it was perceived to be necessary to compete in the market against it's rivals from Europe, such as Jaguar's XKE and the Ferrari 250GTO.
GM also fails to innovate well. The company has been scared to do so since the Corvair debacle, and when they have the products were not well-vetted enough that they should have gone to market in the first place. The Vega's aluminum engine is one example. Instead of using steel or Iron liners like they had in the Corvair and Buick 215, the left them aluminum and iron plated the pistons. Innovative? Sure! Did it actually work? NO! Yet, they made that engine for 7 years and it was the car they expected to be their import fighter. Against competition like the Corolla and 510 it was no match. The Datsun used a high nickel Iron block, forged rods and a forged crank. It gained a reputation for durability that it still is known for today. I know nothing of the Corolla, but I am sure it is a similarly good design. OK, so at least it's replacement was better-right? Not exactly. The Chevette was slow and poorly built. The next generation car was the Citation which....was also a piece of crap. They later re-used the Citation mechanicals and made such lovely cars as the Cavalier and Celebrity ummmm.....yeah. Compared to a Toyota or Honda of the time, they were crude, unrefined cars with too much NVH.
So, in order for GM to gain a market foothold again, it will need to re-think everything. It's whole business model needs to be rethought, and developing good, reliable products capable of being abused with good build quality must be it's top priority. They must not only be good, they need to be exceptional. Otherwise, people like me will not change our purchasing habits and buy new GM cars again rather than the quality Japanese products we are now used to.
