The 59's with the recirculating heater didn't have a shut off valve from the factory. If your core has 3/4 on both rigid lines from the core, somebody did that, it came from the factory with one 5/8's and one 3/4's. I believe the 5/8 was the return flow line into the heater core.
Last edited by Cablesmill; 04/08/2017 7:24 AM.
