Cooling system

[MortamerPA]

Hello, all:

I acquired an '83 K20 off-road truck from a friend.  It was originally equipped with a 6.2L Diesel, but was swapped out for a 454 TBI from a 90s vehicle.  It's a 4 speed manual transmission.  The ECM was fried and my buddy put on an intake and carb, but it hasn't run since.  My question is related to the cooling system.  There is a line running from the heater core directly to the radiator top tank.  A second line is the right length to terminate at the thermostat housing, but wasn't attached when I got the truck.  There is also an open fitting on the water pump.  What I'm used to seeing is a hot line running from the manifold/thermostat housing to the heater core, and line running from the heater core to the water pump, or at least this is how it is on my '82 C10.  I'm perplexed with what is the correct setup and why a line may be run directly to the radiator. 

Sorry - pics were too large to upload.  Any help would be much appreciated.

[bake74]

     In the tech section, under 73-87 GM Pickup Manuals, in the 83 manual starting on page 1A-10 (pg 52), it shows the diagrams for the heater hoses routing.  It has all the different models including Diesel.
     You can read through this and find the one that best suits your truck now.
     Also in the tech section is "how to resize pics" for this forum, or you can host them on a different site and use the "insert image" button above (the one that looks like a pic of Mona Lisa, above the smileys and to the far left) to import the pics.

[MortamerPA]

Thanks so much for your help, Bake74.

[MortamerPA]

The manual suggests a line should run from the heater core to the radiator & another from the intake manifold to the heater core.  There is a hose barb fitting on the top side of the water pump, which I should be able to remove and plug.  Given that it was a former conversion, I wanted to do some h/w.

[bd]

Either return routing will work.  But, if you have the 3/4" hose bib on the radiator tank, use it and plug the water pump port - should be 1/2" NPT.

[roger97338]

Big blocks also have a short length of hose that runs from the water pump to a fitting on the front of the intake manifold. I'm not very familiar with the big blocks, but I think it might be the bypass.

[bd]

Roger97338 is correct.  The exposed W/P fitting is for the bypass and should be connected as illustrated.  The adjacent fitting is the return port that should be abandoned in favor of the radiator tank bib if present.

[MortamerPA]

Thanks for the help, guys.  I will plan on running a line from the water pump to the intake manifold.