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Silverado in Slovenia

Now that The Winter Trial is behind us and Silverado has returned to TwinSpark Central to be serviced, it is time to evaluate how it behaved and what we have learned.

Tyres
We ran Vredestein SnowTrac2 15x6x185 in the front and the same size SnowTrac3 in the rear. The rear tyres were changed at the eleventh hour, when a blister had appeared on one of the 1 year old SnowTrac2’s. The Snowtrac3’s initially felt weak due to their soft side walls, but once the car was fully loaded and we had covered some distance, they seemed firmer. Steering became more twitchy when running without spares, luggage and co-driver and I’m convinced this had to do with the rear tyres in combination with the 26 mm rear torsion bars. Job for the next time: find snow tyres with stiffer side walls, but with the solid traction of this type of profile: we never had to use snow chains!

Gearbox
We drove with a ’74 915 gearbox, fully rebuilt, with a plate-based limited slip differential and the durable 8:35 crown and pinion which TwinSpark Racing sells in its rally products section. The most important characteristics of a rally ‘box are that it is slightly shorter and stays in one piece. It did both of those and LSD was a great help in wriggling through sharp, narrow hair pins in 1st or 2nd.

Engine

The 2.7 RS engine turned out to be the Cat’s Meow. You will have heard in the videos I posted how that thing picks up. We never had it on the dyno so far, but by now I’m quite curious to find out what power and torque it delivers. Initially I had some concerns whether this type of engine would be suitable for an event in which you occasionally need to rely on really low end torque at low speeds, just to avoid the wheels from spinning on snow and ice. As the engine is in such prestine condition after the rebuild, it turned out that my worries were completely unjustified. The MFI fed block started in one go, no matter the temperatures, revved low when we needed it and screamed its little heart out when we needed power all the way to 7.000 revs on the tests. It’s truly versatile and I couldn’t find a thing wrong with it. It’s no wonder people go gaga over this engine in the Carrera RS of 1973.

Suspension

Silverado was delivered as a 1971 T with all the S-options, most of which were retained. We changed the shocks to Bilstein Sport (like the Carrera RS) and changed the rear torsion bars to those of an early Turbo (26mm). Although the shocks could be softer for more traction in the snow, the configuration as a whole is truly multi-purpose. The suspension, with its standard anti-roll bars, is stiff enough to have fun on track, move at speed on the highway or rally on somewhat bumpy roads. When you go full-throttle in second and third you can feel the car squat, despite the stiffer rear torsion bars; imagine how much torque the engine must deliver. Even my old Turbo didn’t squat like this. Because I use the car in all sorts of situations, it all works out well for me. The rally ride height, measured from the ground to the highest point of the fender lip, is 61cm, without luggage or passengers. This allows you to take speed bumps or ditches with reasonable speed without the fear of bottoming out.

Sump Guards

As you noticed in our report on the Winter Trial, we had two off road excursions, landing on top of a snow bank. Having front and rear bottom guards on the one hand put us higher up the banks, making it harder to free ourselves because we slid on due to the smooth bottom surface. On the other hand, the guards lifted us up, allowing us to continue the rally without any damage to the suspension, oil or brake lines, once we were pulled off. I can recommend this solution to anyone doing even moderately serious rallying.

Comfort

When you spend 10-12 hours a day, 8 days in a row, in a small cockpit with a roll cage, a proper pair of seats becomes a must. Granted, we played around with seating positions, particularly for the navigator, quite a bit and found that the co-driver seat should be slightly reclined to ensure the greatest comfort. Perhaps a few degrees, but it made a big difference. I use BF S/T rally seats in leather (even the seating area) and they are the most comfortable, yet sensitive seats you can imagine. Seats are very personal, but these I have found to be the right mix of firmness, allowing for suspension feedback, and support.

Fuel Tank

We mounted the ’74 Carrera 85 liter fuel tank last year and we could cover the entire day of sometimes 450 km without the red light coming on. Certainly a convenient asset when cruising through bear-infested Czech forest terrain at night…. Although this tank only accepts a space saver wheel and we felt we needed to bring an entire spare wheel we had a bit less space in the nose of the car, but we never missed it, since we had made the rear seating area accessible.