Heater Hose Size

[dodgedart1968]

1968 Dodge Dart Slant Six

I'm in the process of reassembling my heater after a complete rebuild. I noticed that the engine heater hose fittings are both 5/8" (thermostat cavity and water pump). The heater core fittings, however, don't seem to match. One is 5/8" but the other is 1/2". This means that the inlet hose (thermostat to smaller heater core fitting) are mismatched. Can anyone explain this?

 

[Dana67Dart]

Is it an AC car?

The larger tube might go to the shutoff valve.

Just a guess.

 

[French demon]

My slant 6 Demon (no A/C) has also heater core fittings of different diameters
I have had to install a smaller ring on the left hose to avoid a liquid leak.

 

[Demonx2]

My slant 6 Demon (no A/C) has also heater core fittings of different diameters
I have had to install a smaller ring on the left hose to avoid a liquid leak.
View attachment 1715934475

A smaller ring? What do you mean? I have this same bridge to cross too. My intake fitting is 1/2" but the heater box is 5/8" so I need to adapt something somehow or sttrreeeettcchh some 1/2" hose over it.

 

[French demon]

A smaller hose clamp on the left hose than on the right one.
The two rubber hoses are identical in diameter, but with a Mopar style spring-clamp, I have no leak.

 

[Oldmanmopar]

up to 1969 they were both the same 5/8 on the heater core. 1970 and newer were 5/8 and 1/2. You installed the newer style heater core and have a older style engine

 

[413]

1970 and newer started the mixed sizes 1/2 and 5/8 of heater hoses. 1969 and back was 5/8” on both.

The fittings on the water pump/intake were matched to the heater core sizes. So when swapping parts this becomes a problem.

look up the reproduction heater hose fittings and see the changes.

Heating & Cooling, Heater Hose Nipples :Mega Parts USA

 

[dodgedart1968]

The heater core had a 1980 date on it. So it was replaced and the hose size was not corrected. I'll use a 1/2 to 5/8 adapter and some 1/2" hose to make it fit.

 

[Demonx2]

up to 1969 they were both the same 5/8 on the heater core. 1970 and newer were 5/8 and 1/2. You installed the newer style heater core and have a older style engine

I think the opposite. The heater core is 5/8 and 5/8 (restored by "the heaterboxguy" out of PA about 2 years ago) and he asked me what core sizes to use. Oops, I told him 5/8-5/8 not knowing my engine had the 5/8-1/2. Now it's time to pay the piper and deal with it. I was just asking if someone makes a rubber bushing or something. I'll either end up with 5/8 hose and the smaller orig Mopar ring clamp or 1/2 hose and get it hot and stretch it over the 5/8 core. Stupid little problems always getcha!!