Heater Hose Question

[1971ChevyTruck]

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]

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]

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.

[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

[El Jay]

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

[El Jay]

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]

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]

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

[1971ChevyTruck]

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...

[El Jay]

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]

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

[chipflyer]

I'm thinking it wouldn't work like I stated. Being the pump pulls cool water in and pushes it thourgh the engine.

Some did dump to the waterpump. I am not sure when they changed it but when the return dumps to the fitting on the water pump it would certainly warm the engine up quicker. You are dumping that warm water from the heater into the suction side of the waterpump and instantly recirculating it instead of just dumping it back in to the radiator and waiting for the thermostat to open.

If anyone knows, I would like to find out when they switched from the radiator to the water pump on the return heater hose or was it connected to the water pump first?

Jeff

[El Jay]

Originally Posted by Sport/Truck

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

"Cool" water is a relative term.
After the engine's up & running, that radiator will be somewheres around 180 degrees, or more.
Remember, the thermostat controls the minimum temperature.

[1971ChevyTruck]

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

[Sport/Truck]

Originally Posted by chipflyer

I'm thinking it wouldn't work like I stated. Being the pump pulls cool water in and pushes it thourgh the engine.

Some did dump to the waterpump. I am not sure when they changed it but when the return dumps to the fitting on the water pump it would certainly warm the engine up quicker. You are dumping that warm water from the heater into the suction side of the waterpump and instantly recirculating it instead of just dumping it back in to the radiator and waiting for the thermostat to open.

If anyone knows, I would like to find out when they switched from the radiator to the water pump on the return heater hose or was it connected to the water pump first?

Jeff

I wonder if recirculating the hot back into the engine will cause it to run hotter? Seems like if your constantly circulating hot water /bypassing the radiator/ it would cause an uncontrollable gradual increase in temperature. (just like you get faster warm-ups)
IE lets say the radiator droops temp by 20 deg. on a hot day.
Now add in a the hot water that would constantly bypass the radiator- I'm thinking it would have a cumulative effect?
(Just ignore me....I usually over think trivial stuff.....lol)
after all this discussion I've decided I'm going to pull water off the intake and dump in the radiator.

[tnblazerk5]

on my 67 the hoses were run to the water pump and intake , the heater worked but would take forever(30mins or longer) to get it in the cab (by the time the cab got warm i would be where i was going lol )
i put a new (well used lol ) 4core in it a few years ago and it had the one on the rad so i blocked the water pump off and ran the hose to the rad and wow what a differance it made !! i got all kinds of heat in the cab now truck seams to run lots cooler now but i also added elect fan at the same time

[chipflyer]

I wonder if recirculating the hot back into the engine will cause it to run hotter? Seems like if your constantly circulating hot water /bypassing the radiator/ it would cause an uncontrollable gradual increase in temperature. (just like you get faster warm-ups)
IE lets say the radiator droops temp by 20 deg. on a hot day.
Now add in a the hot water that would constantly bypass the radiator- I'm thinking it would have a cumulative effect?
(Just ignore me....I usually over think trivial stuff.....lol)
after all this discussion I've decided I'm going to pull water off the intake and dump in the radiator.

I don't believe that dumping into the water pump would make it run hotter, remember thats why we have a thermostat that regulates the temp and doesn't open until the water hits a preset temp.

I am sure there were pros and cons either way. Good discussion!

[JimKshortstep4x4]

The assembly manual shows the routing to the radiator with the V-8's and auto transmission.

Jim