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Home > LATEST STORIES > Roll The Dice—Skinny Kid Race Cars Experiments with Liberty’s Gears 7-Speed for Quarter-Mile Pro Mod Racing | Presented by Nitto Tire

Roll The Dice—Skinny Kid Race Cars Experiments with Liberty’s Gears 7-Speed for Quarter-Mile Pro Mod Racing | Presented by Nitto Tire


You’ll never know if you don’t try it and that is exactly what Keith Engling and his Skinny Kid Race Cars shop are doing with a new transmission configuration for the Richards Auto Parts sponsored 1972 Hurst Oldsmobile replica.

The one-of-a-kind Oldsmobile is normally equipped with a Liberty’s Gears Extreme-T five-speed, which is only run through four gears in eighth-mile racing—more on that later. For their upcoming trip (thanks to Bill Jennings of Lapeer International Dragway) to the Street Car Super Nationals at The Strip at Las Vegas Motor Speedway, the team will be experimenting with a billet-case 7-speed by Liberty’s Gears designed for quarter-mile racing.

“The idea is to keep the shifts short,” explains Engling for the unusual 7-speed configuration of his new Liberty’s Gear transmission setup. The strategy was developed this past summer in the 5-speed version of the transmission as a means to keep the ‘screw-blown HEMI engine in its optimum range of 9,300 and 10,000 rpm.

Engling worked with Craig Liberty and his transmission company to design a gearing package for an Extreme-T 5-speed that only reduced the rpm drop off by 10% of the engine speed—1,000 rpm in this application. Despite the transmission having five gears, the decision was made to only run it through Fourth gear because the final 5.40:1 drive ratio with a 4.11:1 rear and 1.32:1 transmission gear put the engine at 10,000 rpm through the lights for eighth-mile racing. Moving to the 7-speed setup continues with that approach, but accounts for the additional 660-feet of race course for quarter-mile racing.

The PCM on the left is the digital controller by Liberty’s Gears and is programmed using a laptop.

In addition to the performance advantages of the gearing, the team saw the rear gears life expectancy increase and it reduced the amount of stress on the engine from the big rpm drops at the shift. As Engling tells us the 10,000 rpm shift point would need a 5.40:1 rear gear with a 1:1 transmission ratio.  The numerically larger gear offers less pinion teeth, which in some cases would cause rear gear failure in as little as two runs. That is a cost prohibitive situation even in a Pro Mod operation, let alone the uncertainty of completing a run during a race. Moving back to the 4.11:1 rear-end ratio and using Fourth instead of Fifth eliminated that problem, kept the finish line rpm at 10,000 rpm, and the ratios for each gear keep the engine happy. That might sound unconventional but it is hard to argue with the car’s best eighth-mile run of 3.63 at 205 mph.

This is the Liberty Extreme-T 5-speed that is normally run in the SKRC Oldsmobile. It uses a magnesium case while the 7-speed version is only offered in a billet case.

Engling is carrying over his tried and true Neil Chance Racing torque converter to the new 7-speed. The bolt-together torque converter is made from billet and features a lock-up option. The relationship between Neil Chance Racing Converters and Skinny Kid Race Cars goes back over twenty years.

Two years ago the Oldsmobile was rebuilt with a scaled down version of the original carbon fiber body. It is a unique style that has been the calling card for the popular Michigan-based chassis shop. Powering the hot rod is an all-billet HEMI engine that was built by Billy Briggs Racing Engines and it has a massive Twin-screw supercharger sitting on top. Estimated horsepower is in excess of 3,500hp and with a best quarter-mile run 5.71 at 253 mph, we don’t doubt those power claims.

Thanks to sponsorship from Bill Jennings of Lapeer Dragway, the team will be competing in the Street Car Super Nationals November 15-17 at The Strip at Las Vegas Motor Speedway. If all goes according to plan, Dave Hill will drive the Richards Auto Parts Oldsmobile to the 5.50s at over 260 mph.

Here is the Skinny Kid Race Cars Oldsmobile Pro Mod warming up in Las Vegas during last year’s event. It is one of the most unique cars in Pro Mod. Photo by Paul Fercho.

Mike Galimi
Mike Galimi is the Director of Content & Marketing at ProMedia Publishing and Events with nearly 20 years of experience in motorsport writing and photography.