65 C10 heater core removal !!

[jmcap]

1998,

Thanks for the thread referral. Found so many things that were wrongly done. As you noted the wrong size hoses were routed improperly: the intake manifold fitting is 3/4" and going to the "out" side of the core, and the fitting at the water pump is wrongly 5/8" and going to the "in".

Here's the kicker !!

I didn't mention, but pictured above, I found the rubber cap over the 'out' port of the heater core blocking the flow path. Going back after your post I was shocked to find the 'in' port rubber cap within the end of the hose.!!!! Can only assume that the core was replaced at some point and the caps were never removed before attaching the hoses.
I will test for heat tmrw. If successful will buy new hoses, swap out the 5/8" and 3/4" fittings , and route the hoses properly.