What size heater hoses for 58 with Deluxe heat

[62lwbc10]

Hey guys about to install my Delue heat system and wondering what size NPT fittings for my SBC? Is it 5/8" for both hoses?

Thanks,
Mark

[dubie]

one hose is 5/8" and the other is 3/4"

[G&R's57GMC]

Its 5/8" on both hoses on my '56's & '57.

Your heater will determine what size hoses and fittings go on the engine.

[62lwbc10]

Hey TIm thanks thats what someone else told me but both fittings at the heater core are 5/8" What gives?

[G&R's57GMC]

two sizes of heater hose came much later in the 60's

[mr48chev]

Originally Posted by 62lwbc10

Hey TIm thanks thats what someone else told me but both fittings at the heater core are 5/8" What gives?

Probably an aftermarket heater core that works but isn't quite like the original one. Most likely you will have to change the nipple that goes on the waterpump out for one that is for a 5/8 hose and be done with it.

Most all GM anything that I have worked on have the 5/8 hose from the engine to the heater and the 3/4 running from the heater to the water pump or to the radiator in some cases.

Back to the original question I think that both fittings are 1/2 npt in the intake and in the water pump. The one in the waterpump could be 3/4 but I don't think it is and I'm at work so I can't check one of mine to find out.

[62lwbc10]

Very interesting responses. My core definitely looks original and its definitely has both connnections as 5/8". I should say the heater box is from a 55. I have a neighbor who has a totally original 58 step with 50K miles. I will double check what he has. Thanks for all the input

[dubie]

my 56 has both sizes of fitting because the engine is from a 69. The pipes coming from the heater core are both 5/8"

[Daze57]

5/8 one side -3/4 the other -57 bbw