On 1 November 1979, Chrysler announced and commenced sales of the enlarged, 2.6-litre "Astron" engined Sigma GL and SE. At the same time, the 1.85-litre engine was dropped. Paired only with the automatic gearbox, 2.6-litre was believed to be the biggest four-cylinder engine sold internationally at the time. The 2.6 came further equipped a new braking system with larger front discs and a 56 percent increase in pad area. 14-inch cast alloy wheels were also made available as a further option for the 2.6. The 2.6 was noted for its smoothness and refinement, although less so than its 2.0-litre counterpart. Its large displacement made it competitive with six-cylinder rivals. Chrysler claimed of power and torque of . According to Chrysler, this made it the most powerful four-cylinder engine sold in Australia at the time.