Water pump questions

[84prspctr]

I have a sbc 350 with no heater and no thermostat. I just did a coolant flush and new lower hose and found out there’s no thermostat in there. I had my hand over the bottom bung on the rad and put the hose in the rad to flush it and water started coming out of the water pump where the lower hose hooks up, so there isn’t a thermostat I guess. Anyway my water pump just started leaking out of the weep hole after I just changed the coolant so I need to put a new one on. I want to put in a 180 thermostat too. I am not familiar with sbc engines, I know with mopars they have a bypass hose on the water pump for when the thermostat is closed. My truck doesn’t have any heater hoses, just the pump and rad hoses. Is the bypass internal or something on these pumps when the t stat is closed? And what would normally be in this plug on the top of the pump? Thanks

 

[84prspctr]

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[84prspctr]

I am also unsure as to which pump to get because this engine was swapped in. It has headers no smog and Holley intake and is in a 1973 j4000 truck. Should this pump https://www.napaonline.com/en/p/TWP43099

Or this one work?

https://www.oreillyauto.com/detail/c/murray-temperature-control/engine-cooling/water-pump/d916446a6bad/murray-temperature-control-water-pump-new/mtc0/cp1109

 

[84prspctr]

Advance Auto Parts - Down for Maintenance

This one looks to be closest to what’s on there with best reviews. Should it fit as long as it has those alternator mounting holes?

 

[nvrenuf]

The thermostat is under the water neck where the top hose attaches to the intake manifold. I wouldn't worry about the water flushing out of the pump, it's just taking the path of least resistance.

The Napa pump looks right however most of them look VERY similar. I'd buy a pump for something like a '78 "C10" (1/2 ton truck) with a 350, that should fit just fine.

I've never been a huge fan of Cherokees or Wagoneers but the J trucks are sweet, love the rugged feel about them. Post up a pic sometime.

 

[fast 99]

Plug on top of pump is for a different heater hose configuration. Some returned back to the radiator others to the pump. Bypass is internal to pump, extra hole on one side. 73-76 pumps should be the same. Bleed the system when filling, leave the thermostat out, fill until coolant is near top edge of opening, install stat.

 

[84prspctr]

The pump I typed in was for a 75. What’s the difference between the 75 and 78? They look the same ones more expensive. Here’s pics of the truck

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[scrap--metal]

What’s the difference between the 75 and 78?

SBC's used both "long" and "short" water pumps. The casting is different between the two styles, which puts the drive pully on a different plane relative to the mounting surface on the engine block.

Confirm whether your leaking pump is a "short" or a "long", and buy the same style replacement. This video should help. I didn't watch it, but the title seems right.

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[Ricko1966]

Looks like long water pump to me, 1975 c or k 10 with a 350 automatic, ought to be enough info for the parts guy to find you the right pump. A little trick when changing the thermostat put a 1/16 hole in the t stat before install so it doesn't air lock,or wedge the thermostat open with an asprin before you install it,the asprin will devolve after you get it running. The reason I put a small hole in my own junk I never have to worry about an air lock in the future if I have to drain and fill etc.

 

[Ricko1966]

SBC's used both "long" and "short" water pumps. The casting is different between the two styles, which puts the drive pully on a different plane relative to the mounting surface on the engine block.

Confirm whether your leaking pump is a "short" or a "long", and buy the same style replacement. This video should help. I didn't watch it, but the title seems right.

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Long and short happened in 1968.

 

[Turbo4whl]

Plug on top of pump is for a different heater hose configuration. Some returned back to the radiator others to the pump. Bypass is internal to pump, extra hole on one side. 73-76 pumps should be the same. Bleed the system when filling, leave the thermostat out, fill until coolant is near top edge of opening, install stat.

This is a good plan. The engine can get an air pocket at the thermostat. Hot air will not open the stat, only hot water/coolant. I also like to drill a small hole in the stat, bleed hole, so there will not be an air pocket. Some thermostats have the hole or notch to bleed air, many do not.

 

[75gmck25]

If you buy a high flow thermostat, the ones I’ve used already have the bleed hole in them. They are usually in the aftermarket parts area in the store, or you can get them from Summit, Jegs, etc.

Also, if you have a relatively stock engine application, i suggest using a 195 degree thermostat, not a 180 or a 160. Street engines work much better and stay healthier running at 195-200 (or even up to about 220) .
Also, remember that a low temp thermostat will not fix an inadequate cooling system. The best it can do is to delay the overheating a few minutes. A squarebody with a good radiator, water pump, and the stock steel fan and thermostatic fan clutch has a lot of cooling capacity. Just makes sure it’s all working as designed.

 

[84prspctr]

It is a long pump so I picked up that Murray one from o Reilly. It seems ok quality and spins smooth and firm. I got a 180 Murray thermostat too. It is going to get to be 115+ this summer so I figured it would get hot quick enough. Where do I drill the hole in the thermostat? Is 1/8” too big?

 

[84prspctr]

i flushed that cooling system with a hose and let it run until it was clear coming out of the block and rad. The rad is bigger than factory and has 3 or 4 rows. I also used 2 bottles of that Prestone cooling system cleaner and protectant and ran it for an hour. I then flushed it again and mixed Prestone all vehicle concentrate 50/50 with distilled water. The cooling system is really clean the water was crystal clear. The only junk that might be in there is sediment and rust at the bottom of the block. The trans cooler is and air cooler so that isn’t a factor for heat in the engine. I am hoping I don’t have any issues with over heating now that I’m putting in a t stat. It ran on a colder night 65 degrees out at like 130 climbing the Cuesta grade at half throttle going 65 and on a hot day with just water before I flushed the cooling system at 180 in traffic.

 

[84prspctr]

If you buy a high flow thermostat, the ones I’ve used already have the bleed hole in them. They are usually in the aftermarket parts area in the store, or you can get them from Summit, Jegs, etc.

Also, if you have a relatively stock engine application, i suggest using a 195 degree thermostat, not a 180 or a 160. Street engines work much better and stay healthier running at 195-200 (or even up to about 220) .
Also, remember that a low temp thermostat will not fix an inadequate cooling system. The best it can do is to delay the overheating a few minutes. A squarebody with a good radiator, water pump, and the stock steel fan and thermostatic fan clutch has a lot of cooling capacity. Just makes sure it’s all working as designed.

I do not think it is stock. It’s worn out with less than ideal oil pressure, I was told to run 20w50 with rislone zinc additive to help with that now I get 18lbs hot idle 50 cold 28 running 2200 rpm down highway, but has tons of power and will rev to 6500 rpm with a touch of the gas.