"Pierre (Joubert) and Theo (Oosthuizen) each had a 1966 Opel Rekord, real dogs GM was then building under rising apartheid's local content programme, with primitive 2.1 litre 4 cyl Chev engines. The Chevy four was a chopped down version from the very successful Chevy sixes of the time, but suffered from excessive second harmonic vibration, a characteristic that is otherwise cancelled out in a six cylinder version of the same engine, or reduced by longer con rods. This engine not only had poor performance for it's size, but self destructed hang on parts like air cleaners and alternator brackets, all of which were later suitably beefed up. Many four cylinder engines have balance shafts to counteract this condition, but GM did'nt know about that at the time. or if they did, just accepted that a bit of vibration in a low revving tractor engine did'nt really matter
The Chevy could push the Rekord to around 140km/h, and with a compression ratio of 7.1 those Chevy's could probably have run on paraffin. This was part of a disasterous engine swop program GM had hurriedly embarked on when they threw millions at an otherwise very sophisticated engine plant. The low compression ratio was because in their mixing and matching of parts, a cylinder head with combustion chambers suiting the 230 six cylinder engine was accidentally placed on a block with bore sizes from the 194 six. They also made a gross error in downrating the diff ratio from 3.55 off the older Rekord with a smaller 1.7 litre German engine, to 3.67, when a far more suitable 3.08 ratio was available. This kind of thing happens when product engineering takes place in the front office between accountants and parts bin managers
The previous P3 Opel Rekords with their German engines had been in number 3 slot in sales, but with the Chevy engines Opel and GM's market share went into free fall. Theo and Pierre were both Opel lovers. Theo from a loyal GM supporting farming family, and Pierre an engineer in the said new engine plant, were distressed at that. So they set out to prove the cars could do better and started tinkering and tweaking, first raising the compression ratio by skimming a massive 3.5mm off the head, which made an immediate improvement, and then doing all the other things. They ran a sort of competition between themselves, both cars ultimately breaking the "ton" (160km/h). Impressive at the time, before the hot"
"Theo's Rekord was tested by Car (July 1967) click on pic to see report. Car was highly complimentary of Theo's Opel
GM eventually made a number of improvements to the Chevy engine through their own lumbering procedures but they never really recovered their position. They followed our example by raising the compression to 8.4:1 and later fitted an eight port head with Weber carbs. They also ran an incentive campaign to retrofit existing cars with Webers. They increased capacity to 2.5 litres by adopting the 230 bore size, and still later, down to 2.3 by shortening the stroke. The shortened stroke was a good move and reduced that second harmonic (which derives from the angularity of the conrod as the gurus would say). It became an OK engine for the time, but GM had damaged their reputation, and other things had happened in the market, like the growing Japanese presence and the growth of Mercedes and BMW. The Chevy four none the less continued in the GM family for a long time, in the US a Pontiac version later was known as the Iron Duke. There was controversy over the Pontiac version's relationship with the original Chevy version
The sad ending for South Africa is that during the time of disinvestment in the 1980s, the fickle GM management decided to can the South African engine plant. It was first mothballed and later all that wonderful machinery was sold for scrap on an auction that lasted two days. At the other end of town GM's long time rival, Ford, also had an engine plant, but they bit the bullet, retooled their plant and to this day it is in production serving the local and export markets."
Source: www.septua.co.za/pierre_joubert_files/sunpacer_car.htm
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