This is a mod I made for my 1986 IROC-Z. During AC operation, hot coolant flows through the heatercore. I eliminated the coolant flow during AC operation to optimize my AC. From 1987 and above, there is a valve ( https://www.partsgeek.com/9sd3cbs-chevrolet-camaro-heater-valve.html?utm_source=google&utm_medium=ff&utm_content=DN&utm_campaign=PartsGeek+Google+Base&utm_term=1987-1992+Chevrolet+Camaro+Heater+Valve+GPD+8211260+87-92+Chevrolet+Heater+Valve+1991&fp=pp&gbm=a&gad_source=1&gclid=CjwKCAjwxNW2BhAkEiwA24Cm9ImtFSu84CcBHMJDpGA8ZbueU9mYXKizLvBcWBpN8FM77nLd7tKL9BoC5PMQAvD_BwE) that redirects hot coolant from the heatercore to a tube on the right-side frame rail which routes the coolant back into the radiator. Along with this setup, the hvac controls and the vacuumlines for the HVAC differ from 1986 and below. So instead of going to the junkyard to get this frame rail heater tube that has the additional fitting for rerouting the coolant back to the radiator, later version of HVAC vac lines, and the HVAC control unit, I tapped into the cabin air door for cabin recirculation as it has vacuum only on Max AC. This vaccum is what controls/shuts the flow of coolant from circulating into the heatercore.

 

 

Cut into existing vacline for the interior circulation.

Cut into existing vacline for the interior circulation.

Vacline heading into fender area using the existing antenna cable grommet.

Ford valve.

Ford valve.

Install completed.

Rounting of vacline.

Rounting of vacline.

What us 86 and early 3rd gen owners dont have.

87 above heater hose valve.