Heater Hose Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1971ChevyTruck · 03-10-2008, 05:53 AM

I have a motor out of a new truck in my 1971. Before I bolted my front clip on I ran the heater hoses from the water pump to the heater core and from the intake to the heater core. I installed the radiator and noticed there is a heater outlet on the radiator. It looks to the the one for the 3/4" hose. So should I unscrew the fitting on the water pump and buy a plug---then use the one on the radiator?? Will this circulate properly??

**El Jay** · 03-10-2008, 06:33 AM

I'll be honest. I don't know if I'm going to help you, or mess you up.

I just wandered outside (w/in the last 2 mins.) & looked @ my stuff.

On my '69 Chevy, SB: it's 3/4" from the water pump to the heater core.
5/8" from the heater core to the intake manifold.

On my '72 GMC, BB: it's 5/8" from the manifold to the heater core.
3/4" from the heater core to the radiator.

Since your radiator is set up for the 3/4' hose, I'd personally go like the '72, & put a plug in the water pump.

You now have my .02; & honestly, that's really all it's worth.

El Jay

neonlarry · 03-10-2008, 06:33 AM

That will work fine. I'm not sure when GM started that my 70 had WP outlet, my Burb had radiator outlet. I say had as in past tense because when I went to the serp setup on my 70 those water pumps don't have an place for the heater hose.

**El Jay** · 03-10-2008, 06:46 AM

Quote:

Originally Posted by neonlarry

That will work fine. I'm not sure when GM started that my 70 had WP outlet, my Burb had radiator outlet. I say had as in past tense because when I went to the serp setup on my 70 those water pumps don't have an place for the heater hose.

This is really a moot point, but I think the free flow of information benefits all of us.

The heater hose to the radiator is the "return" line, because in the olden daze, before recovery systems, the hose barb on the radiator could very well be above the water level; so there would be no water going to the heater core.

Enjoy what's left of your weekend.

El Jay

Sport/Truck · 03-10-2008, 06:42 AM

Somebody please correct me, but I'm pretty sure the original location is in the water pump to the lower heater hose out the top of heater core to the fitting on the radiator.
I think most people use the intake because the fitting for the water pump wont fit. Thats my dilemma but going to make a SS fitting this week.
s/t

**El Jay** · 03-10-2008, 07:00 AM

Quote:

Originally Posted by Sport/Truck

Somebody please correct me, but I'm pretty sure the original location is in the water pump to the lower heater hose out the top of heater core to the fitting on the radiator.
I think most people use the intake because the fitting for the water pump wont fit. Thats my dilemma but going to make a SS fitting this week.
s/t

I'll be honest.
I don't know when the "change" took place.

On my '69, I had the radiator rebuilt; i.e., new core using my factory tanks.
My '72 still has the factory set up in it.

Any input from somebody smarter than I would certainly be appreciated.

Sport/Truck · 03-10-2008, 07:23 AM

Quote:

Originally Posted by El Jay

I'll be honest.
I don't know when the "change" took place.

On my '69, I had the radiator rebuilt; i.e., new core using my factory tanks.
My '72 still has the factory set up in it.

Any input from somebody smarter than I would certainly be appreciated.

It probably wont matter if the hose comes off the intake or pump it's still the supply line. I'm trying to make mine looks orginal, and thats the only reason to make the ss fitting I need.
s/t

chipflyer · 03-10-2008, 07:38 AM

The 5/8" fitting on the Intake manifold (hottest water), is always the pressure or flow line. It goes from there up into the bottom of the heater core, (lets remember heat rises) and returns out of the 3/4" fitting (return lines are always bigger than pressure) at the top of the heater core to either the intake side of the water pump or to the 3/4 fitting on the radiator. If I were you I would buy the plug,(auto parts help section) and return the coolant to the radiator fitting. If you hook it up wrong it will work, but you will complain later that the heater doesn't get very warm or that you have air in the the system that you can't get rid of.

This needs to be in the FAQ section, it gets asked a lot.

Jeff

**El Jay** · 03-10-2008, 08:06 AM

Quote:

Originally Posted by chipflyer

The 5/8" fitting on the Intake manifold (hottest water), is always the pressure or flow line. It goes from there up into the bottom of the heater core, (lets remember heat rises) and returns out of the 3/4" fitting (return lines are always bigger than pressure) at the top of the heater core to either the intake side of the water pump or to the 3/4 fitting on the radiator. If I were you I would buy the plug,(auto parts help section) and return the coolant to the radiator fitting. If you hook it up wrong it will work, but you will complain later that the heater doesn't get very warm or that you have air in the the system that you can't get rid of.

This needs to be in the FAQ section, it gets asked a lot.

Jeff

Good points, Jeff.

The only thing that I would change is go to "Ace is the place", or some other hardware store for a pipe plug.
Much cheaper there.

Enjoy the rest of your weekend folks.

El Jay

Sport/Truck · 03-10-2008, 08:35 AM

Quote:

Originally Posted by chipflyer

The 5/8" fitting on the Intake manifold (hottest water), is always the pressure or flow line. It goes from there up into the bottom of the heater core, (lets remember heat rises) and returns out of the 3/4" fitting (return lines are always bigger than pressure) at the top of the heater core to either the intake side of the water pump or to the 3/4 fitting on the radiator. If I were you I would buy the plug,(auto parts help section) and return the coolant to the radiator fitting. If you hook it up wrong it will work, but you will complain later that the heater doesn't get very warm or that you have air in the the system that you can't get rid of.

This needs to be in the FAQ section, it gets asked a lot.

Jeff

Ok, you have me rethinking my hose routing.....I basically said the same thing, but wasn't to clear about the hot water flowing out the top of the heater core into the radiator.
But after reading what you said, I'm thinking it wouldn't work like I stated. Being the pump pulls cool water in and pushes it thourgh the engine.

Now I'm wondering where I got the idea it was from the water pump.(I think it was a picture of an original engine.)

Thanks,
s/t

1971ChevyTruck · 03-10-2008, 07:41 AM

Thanks all for the quick responses...I am wanting to fire this beast up in the worst way...after tracking donw the missing hot wire I am ready to go...

1971ChevyTruck · 03-10-2008, 08:13 PM

Wow just got the fitting removed from the water pump---that defiantly has been there awhile--had to use a 3' cheater bar. I am off to Ace to buy a plug--thanks for all the input

03-10-2008, 05:53 AM	#1
1971ChevyTruck Registered User Join Date: Jan 2005 Location: Illinois Posts: 1,006	Heater Hose Question I have a motor out of a new truck in my 1971. Before I bolted my front clip on I ran the heater hoses from the water pump to the heater core and from the intake to the heater core. I installed the radiator and noticed there is a heater outlet on the radiator. It looks to the the one for the 3/4" hose. So should I unscrew the fitting on the water pump and buy a plug---then use the one on the radiator?? Will this circulate properly??

03-10-2008, 06:33 AM	#2
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: Heater Hose Question I'll be honest. I don't know if I'm going to help you, or mess you up. I just wandered outside (w/in the last 2 mins.) & looked @ my stuff. On my '69 Chevy, SB: it's 3/4" from the water pump to the heater core. 5/8" from the heater core to the intake manifold. On my '72 GMC, BB: it's 5/8" from the manifold to the heater core. 3/4" from the heater core to the radiator. Since your radiator is set up for the 3/4' hose, I'd personally go like the '72, & put a plug in the water pump. You now have my .02; & honestly, that's really all it's worth. El Jay __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck Last edited by El Jay; 03-10-2008 at 06:34 AM. Reason: grammar

03-10-2008, 06:33 AM	#3
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,745	Re: Heater Hose Question That will work fine. I'm not sure when GM started that my 70 had WP outlet, my Burb had radiator outlet. I say had as in past tense because when I went to the serp setup on my 70 those water pumps don't have an place for the heater hose. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

03-10-2008, 06:42 AM	#5
Sport/Truck Sierra Grande Club Join Date: Jan 2007 Location: New Mexico USA Posts: 2,433	Re: Heater Hose Question Somebody please correct me, but I'm pretty sure the original location is in the water pump to the lower heater hose out the top of heater core to the fitting on the radiator. I think most people use the intake because the fitting for the water pump wont fit. Thats my dilemma but going to make a SS fitting this week. s/t __________________ 1971 GMC Sierra Grande, 1/2 ton short wide, original 4 bolt 010 020 block & heads. (matching #'s). 383 stroker, SMI q jet 750 cfm, Lunati Voodoo 60102 cam, Scorpion roller rockers, Spin Tech pro street mufflers with X pipe.

03-10-2008, 07:38 AM	#8
chipflyer Registered User Join Date: May 2004 Location: Topeka, Ks Posts: 2,293	Re: Heater Hose Question The 5/8" fitting on the Intake manifold (hottest water), is always the pressure or flow line. It goes from there up into the bottom of the heater core, (lets remember heat rises) and returns out of the 3/4" fitting (return lines are always bigger than pressure) at the top of the heater core to either the intake side of the water pump or to the 3/4 fitting on the radiator. If I were you I would buy the plug,(auto parts help section) and return the coolant to the radiator fitting. If you hook it up wrong it will work, but you will complain later that the heater doesn't get very warm or that you have air in the the system that you can't get rid of. This needs to be in the FAQ section, it gets asked a lot. Jeff Attached Images __________________ I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241. Last edited by chipflyer; 03-10-2008 at 07:40 AM.

03-10-2008, 07:41 AM	#11
1971ChevyTruck Registered User Join Date: Jan 2005 Location: Illinois Posts: 1,006	Re: Heater Hose Question Thanks all for the quick responses...I am wanting to fire this beast up in the worst way...after tracking donw the missing hot wire I am ready to go...

03-10-2008, 08:13 PM	#12
1971ChevyTruck Registered User Join Date: Jan 2005 Location: Illinois Posts: 1,006	Re: Heater Hose Question Wow just got the fitting removed from the water pump---that defiantly has been there awhile--had to use a 3' cheater bar. I am off to Ace to buy a plug--thanks for all the input Last edited by 1971ChevyTruck; 03-10-2008 at 08:15 PM.



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