rgbau140

Does any one know why one hose is 3/4" and the other is 5/8"? Seems odd they are the same size. Unless they are that way so the hoses weren't crossed and connected in reverse? Which makes me wonder if the water flow through the heater box is of any concern?

buns

GM used 5/8" hose on the inlet, and 3/4" on the outlet. Apparently it was done that way so pressure would not build up in the heater core. The only other one I've come across that did this was International.

wmf62

if you have a control valve on the inlet side, water flow direction would make a difference; otherwise, in my opinion, no difference.
Bill

MikeM

I think I remember the '55-'56 Chevy had 5/8" on both nipples. Also think I remember the larger hose came along in '57 on the Pass car?

It must make some difference but I have no idea what it would be.

JohnZ

The 3/4" hose on the core outlet back to the water pump inlet (started in '58, I think) meant that there was always less pressure at the core outlet than at the core inlet, which helped maintain steady flow through the core without making "gurgling" noises inside the heater case.

SunsetC6

3/4" and 5/8" hoses were used in 1959 and later. 1958 and earlier used 5/8" on both. All I know is the 59's are a PITA with the 3/4" and getting it through the firewall. Just finished the heater box on the 59' the other day. It is a tight fit.....