Heater Hoses

[gbskunk2006]

***1986 GMC C15 Full Size P/U with 4.3 Litre V6 (No A/C)***

I noticed that the two outlets for my heater core have different diameters (e.g. 5\8 and 3\4 inch - see URL link below to see image). I'm assuming that each outlet must be either connected to the manifold or radiator and should NOT be switched?  Since owning my truck I haven't needed to replace the hoses but when I finally detached them this weekend it appeared that they are reversed (i.e. smaller diameter hose connected from manifold to larger diameter outlet on heater core and vice versa).  I've owned my truck now for a couple years and the heater has always worked fine and engine never over heated.

Info on the correct placement of the hoses is much appreciated!

Cheers

http://www.classicparts.com/prodinfo.asp?number=68-235

[dumbucket1]

I'm no expert but I can't see any harm for the coolant to flow through the heater core in reverse.

[VileZambonie]

The top one goes to the radiator and the bottom one is fed hot coolant before the radiator (typically from an outlet on your intake). Hotter fluids rise so to increase the efficiency of the heater core the bottom should be the inlet (keeps the core hotter longer for better heat exchange)