Firstly I had to find a partner in crime to help with the build and then had to get management in the service w/shop on-sides. The first turned out to be easy, there were a few trainees with petrolhead tendencies and Trevor was immediately keen, I offered the ¼ mile drive to him as an incentive, I was quite happy to keep running the Kadett myself. Trevor ‘volunteered’ in a flash and the team formed as quickly as that. The second task had to be handled carefully simply because we needed our management in the service dept to support the programme. It was a question of approaching the right guy first, so Harry Schwarz the senior foreman was pulled aside and brought into the picture. He too was ‘in’ like a shot and he came up with the covering story that we were preparing a styling buck for the studio and building it in an unused paint shop. He was great because our normal workshop loads were adjusted and Trevor allowed to spend part time eventually working on the car.
The deal between us was that I would prepare the engine gearbox and axle main components and Trevor would take care of the vehicle prep and build. It worked a treat from the get-go and we worked two or three nights a week and Saturdays. For two youngsters to have such an opportunity was fantastic…… so neither of us were going to screw this up by not giving the full beans. Looking back now I am in fact amazed at the way we went about the thing for two absolute greenhorns. The decision to build the machine as a ¼ mile car made the choices surrounding the chassis and brakes absolutely straightforward…. but the engine and drivetrain took some head scratching. I had only ever race-prepped the 1000cc engine in my Kadett and tuned good numbers of GM streetcars. I had ties with one or two Product Engineering folk who had been involved in engine tuning on the big four cylinder Chevy in recent times but was not impressed with any of the executions or the power they produced, so a different plan had to be made. As far as the transmission was concerned….that was easy. The standard Opel based four speed gearbox suffered a similar awful ratio selection (though not quite as bad) as is found on the British Fords of the time…the dreaded ‘Dagenham gap’…that appalling hole between 2nd and third gears on all small Fords. This could only ever have been specced by a drunken transmission engineer on cocaine.
For my sins I had spent a lot of hours in my spare time devouring specification manuals on all GM product stashed away in every conceivable corner of the business. In the process I found a talent that has served me well over the years. I was a walking GM specification manual. Technicians in the workshop never referred to books when I was around…whether it was a valve spring pressure, head torque, or gear ratio you wanted…..done. As a consequence, I had the information of every available special part in the GM kingdom right on hand….and Opel Germany built a close ratio ‘box under the title “Heavy duty option” (not bold enough to say Competition Option) almost unnoticed in the subtext of a Commodore parts manual…..I ordered one simply by issuing the part number quoted and not telling a soul…..perfect….. R600 off the budget.
We’ll get to the engine which is the best bit, but the next task remained the rear axle and particularly the choice of final drive and installation of a limited slip differential. Again staying abreast of what was happening in the company at a tech level paid dividends. Our engineering ‘buddies’ were just at that time busy with the chassis work on the new 38/4100 range to be launched two years down the line. The new car was to be a development of the Rekord/Ranger, newly styled but to be available with six cylinder engines. The floorpan of the old and new were basically common…and I knew that sample (bigger) model 78 rear axles from Borg Warner were undergoing fitment trials on the new cars…so I asked if there was a spare one. There was. Borg Warner had sent three axles with varying pinion angles for final check…one was hopelessly out and scheduled for the junk box…it found its way to the project instead, free. It was then sent back to Borg Warner to have a 4:1 final drive installed and a limited slip unit. Not free… R400. We adjusted the pinion angle to suite the application and half the budget was now done. There were three reasons for selecting the larger axle: 1. Axle ratio availability, 2. limited slip availability and 3. the use of 5 stud sideshafts to take the proposed wider-tyred 14”wheels.
The engine needed a completely different approach to the job done by product engineering. The team there had followed the rather stereotyped standard of the time applied on small four cylinder engines, by using twin sidedraught carburettors on stub manifolds…bolted to 8 port cylinder heads from the 3 litre Mercury Marine version of the engine. This looked like trying to make this engine a revver….that was not going to happen so I went the opposite way entirely using the 2.1 litre (130) six port small chamber cylinder head…..seriously ported and modified…..I had more sins…. and was bloody good with cylinder head mods. 100 hrs work produced a masterpiece….. it looked nice anyway. My view was that as a first stab this had to be an engine with big mid-range torque as the primary characteristic. The engine came out at 2563cc with flat top forged 283 V8 pistons (found after a search through our parts department) and starting static compression ratio of a moderate 10.5:1. (best I could get with flat tops)
For the camshaft I had thought of a magical Isky of sorts but the budget looked a little sick after the purchase of a brand new 48IDA Weber Downdraught, so it was a call to Basil at Superformance. Along came a TR 71 at just R100…a 298 degree duration profile used on 1600 race Fords of the time. Put to work in the Chevy with a higher 1.75:1 rocker ratio raised the 10.5mm lift to a more respectable 12.4mm in the big engine. Little did I realise that the consequent increase in valve accelerations would give us some initial grey hairs in valve train surge.
The use of the 48 IDA on long runner inlets to the siamesed ports just seemed to be a sensible starting point. We put the engine together by first running the new sub using stock hang-on parts, cylinder head and cam. I wanted to do this to get a good idea of stock rear wheel horsepower before we installed the good bits, as well as getting a squizz at the bores after run in.
The before: 72 Bhp @ 4300 Rpm. (90BHP flywheel)
The after 130 Bhp at 5300 Rpm. (162BhpFlywheel)
We had run into a valve surge problem at 5350 despite running decent small-block springs good to 7000 on the V8. Those valve accelerations were partly to blame and I quickly learnt how to tighten up on the system with guide plates and larger dia pushrods which solved the problem….. but not before we were forced to run the car in its first ¼ mile….. just as it was.