The 1983–84 Hurst/Olds and 1985–87 4-4-2s are distinguishable by there being a "9" as the engine code found in the 8th character of their VINs. These were the only models to get the hotter VIN 9 307 cubic inch engine, and it was the only engine available. From 1983–1985, this engine was flat-tappet valve train, and rated at 180 hp/240 lb•ft torque. In 1986, the 307 engine received a roller-camshaft valve train and new swirl-port heads to improve economy and low-end torque. HP dropped to 170, with torque climbing to 255LBS FT. The 1985 4-4-2 used an OZ code THM 200-4R transmission (as did the 1983–84 Hurst/Olds). Both 1986 and 1987 4-4-2 used the KZF code THM 200-4R. The KZF removed much of the shift harshness of the original OZ coded transmissions, but were still firmer than the run-of-the-mill overdrive transmissions used in the rest of Oldsmobile's lineup.