It's been a while since my 1973 Triumph TR6 graced the pages of this fine magazine. I'm pleased to report the time away has been well spent. Since the last installment (ec, April 2006), I've fixed most of the TR's perennial problems. And of course, added more power.
One of the more unsettling IRS TR traits is rear torque steer, which occurs at the most inopportune times. As the car is wound up, usually shifting from second to third, the tail will lurch to the right. The combination of stock trailing arm bushings and open differential amplified this behavior. Fortunately, the Moss Motors catalog is chock-full of solutions, so I ordered upgraded Prothane bushings and mated them to Goodparts adjustable trailing arm bushings, allowing a greater range of camber adjustment than the standard frame shims. The final piece of the rear-steer dilemma was solved with a Quaife ATB differential, which distributes the brunt of the torque to both halfshafts, rather than shunting it to one unsuspecting and unprepared trailing arm.
With rear steer under control, I went on the quest for more power. As luck would have it, Moss Motors had been developing a bolt-on supercharger kit. My car was used as the R&D mule and, over the course of a year, it was taken apart, measured, poked, prodded and fine-tuned. With an additional 40 hp and 35 lb-ft of torque at the wheels, the car is a newfound joy. Since then, I've driven thousands of miles of California back roads, hooning to my heart's content. Supercharging fits the straight six perfectly, with a broad and instantly accessible powerband. The only downside to all this project progress is the pile of accumulated parts waiting to go on, including a fresh set of GTS Classics seats. Since I'm already having so much fun, I'm reluctant to take it apart any time soon, but keep an eye out for future upgrades and more in-depth information on the supercharger.