Ok, found the article in the back of the 2006 March Mustang Monthly labeled “Core Under Pressure” The guy has a 67 Mustang with a 390 and replaced the heater core twice and now it’s leaking again.
Mustang Monthly states the heater core was damaged from excessive flow, causing them to swell until they leak. They say the factory control for the coolant flow to the heater core is varying the shape of the heater-hose fitting in the intake manifold.
So, this just threw up a flag for me to do something about my fitting before my heater core starts leaking.
1969 Mach1 428 4-speed 3:89 gears,
31 spline posi "N" case, ported edelbrock heads,
full length headers, 292H Comp cam, 750 holley.
Born July 17, 1969
2002 SVT Lightning, Supercharged
1959 Alfa Romeo Giulietta Spider Veloce