Water pumps and heater hoses

[wilkin250r]

My question is more about water pumps than anything. I'll admit, I haven't done all of my own homework yet, but I'm starting the thread anyways.

How do you guys have your heater hoses routed?

From what little I've seen, the short pumps have the main water inlet from the radiator, and also a smaller inlet at 9 o'clock (looking directly at the front of the water pump) that is ideal for a heater hose. This would be ideal, but my problem is I have a long pump, and as far as I know, the long pumps don't have that same smaller inlet on the side.

Is there a brand of long-shaft water pump that DOES have an inlet on the side? Is there an inlet somewhere else that I don't know about (I'm not an expert).

What would I need if I wanted to switch to a short shaft?


I picked up an old beater 79GMC a while back, and it's a slow project. My next phase is getting the heater working. I'm assuming it had an engine swap at one point, and the builder just clipped the lines at the heater core, and never ran any lines out from the new engine. The heater core is there, but the lines from the engine are not, so I'm working with a clean slate.

[ray_mcavoy]

Hi wilkin250r,

Most all the long water pumps I've seen have the heater hose connection near the top 12 O'clock position and angled back towards the engine a bit. Hooking a 3/4" hose to that location and running it along near the back edge of the alternator bracket ends up making it run pretty much right alongside the 5/8" hose that goes to the front/right corner of the intake manifold.

Another alternative (that was quite common on these trucks from the factory) has the 3/4" heater hose going to a connector on the right side tank of the radiator. And a pipe plug in the water pump. The smaller 5/8" hose still goes to the intake.

To convert from a long to a short water pump you'll need a complete set of pulleys, brackets for the alternator, as well as brackets for any accessories you have such as power steering or AC. Just be aware that there were quite a few different OE short water pump bracket setups used over the years and many of them have the alternator on the driver side (opposite of most long water pump bracket setups). You might also need to add a fan spacer or extend the fan shroud so the fan sets in the proper distance.

[wilkin250r]

And the fitting at the 12 o'clock position is an inlet, not an outlet?

[wilkin250r]

I've seen heater hoses return to the radiator. I wanted to avoid that because the most efficient heating will come from engine circulation alone. Returning to the radiator is all well and fine while you're traveling under load and the engine is producing heat. However, it will take longer for the heater to warm up because any heat the engine produces will be circulated and shared with the radiator, rather than just the heater core. Also, when the engine is not under load (like extended downhill runs), you're dissipating all that heat in the radiator, but not producing any in the engine. That's great for your engine, but doesn't keep you warm in the cab.

My mornings are cold, I want to heat up as quickly as possible. Before I'm fully up to operating temperatures and the thermostat opens up, I don't want to circulate warm water back into the radiator to cool off, I want to return it to the engine to stay warm.

My commute is also a short uphill run, then a LONG downhill run. The heater in my daily driver is cold by the time I reach the bottom, I'd bet dollars to doughnuts that my thermostat is closed. I'm hoping with this truck, with the engine circulating only through the heater core, I will get enough heat out of it to keep my cab warm.

[mcboomport]

Wilkin? From atvriders?
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[wilkin250r]

Originally Posted by mcboomport

Wilkin? From atvriders?
Posted via Mobile Device

My cover is blown!!!

Yes, the very same. I'm pretty knowledgeable when it comes to them little machines, but not quite as much when it comes to these big machines. If you searched around a little on ATVRiders, you would find pictures of that very same truck. I got it a year or so ago, but getting it titled has been a nightmare.

[mcboomport]

Haha. Sorry to jack your thread. It's good to see you on here. I also can't wait to see you build a squarebody.
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[irishman999]

Hello from reno!

[one low c10]

you dont need pulleys and brackets to switch to a short pump, they sell water pump spacers to make up the difference. you can buy them for around 12 at just about any speed shop. easier and cheaper than switching everything else

[ray_mcavoy]

Originally Posted by wilkin250r

And the fitting at the 12 o'clock position is an inlet, not an outlet?

The 12 o'clock fitting on the long water pumps is an inlet. So is the 9 o'clock fitting on the short water pumps.

The fitting on the intake manifold is an outlet. So hot coolant flows out of the intake, through the heater core, and returns to either the water pump or radiator.

On the stock setups that have the heater return going to the radiator, it's connected to the same side/tank as the water pump inlet. So the coolant that has gone through the heater core gets drawn right back into the water pump (doesn't go through the radiator core).

Originally Posted by one low c10

you dont need pulleys and brackets to switch to a short pump, they sell water pump spacers to make up the difference. you can buy them for around 12 at just about any speed shop. easier and cheaper than switching everything else

Seems to me like there would still be some issues when using those pump spacers along with brackets off a long water pump. A short water pump doesn't have any of the mounting bosses cast into the housing that are required to attach the stock long pump style alternator and PS pump brackets (pointed out by the arrows in this pic)