In 1986, the IROC received slightly different engine packages. The 86 IROC is the armpit of the entire run. The 305 block in 1986 now had a one piece rear main seal. The TPI 305 was the lucky recipient of the LG4 camshaft, and the result was a drop of 25 horses and almost a half second longer run to 60mph. Chevrolet did allow 50 IROCs out the door with the 220hp L98 350. Beware when somebody sells an 86 as a stock 350. CHECK THE VIN for accuracy. Chevy also let an undisclosed number of these cars out with the T5 five speed transmission as part of the 1LE racing option that also included air conditioning delete, radio delete, as well as the deletion of all power accessories. The 1LE option was not available with T-tops, but did come with specially calibrated springs, shocks and sway bars.

Visually, not too much changed on the 86 IROC. The government mandated 3rd brake light found its way to the top of the rear hatch near the roof line. Curiously, rear window louvers became a factory option this year. Some of the 86 IROCs came with the new 140mph speedometer. 86 was also the first year for the base coat/clear coat paint system as standard equipment.

source : http://www.iroczone.com/history.asp