(Pic) Heater hoses and control vac lines

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December 19th, 2005, 6:33 PM

MudHawg

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(Pic) Heater hoses and control vac lines

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I recently bought my wife a 1985 K5 Blazer. The heater core was bypassed and I wanted to get the heater working again.
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I installed a new heater core and I am also replacing the radiator, water pump and hoses.
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I have a few loose ends that I would like to find out their original connections.
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First, I am replacing the heater hoses and I measure at the core the lower hose at 5/8” and the upper hose at 3/4”. Which hose goes to the intake manifold and which hose goes to the radiator? Does it matter which hose goes where?
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Is there a vacuum or cable operated shut-off valve in one of the lines from the heater core to the intake/radiator? If so, which line gets the valve, which line is the supply line and which line is the return line? 
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In the picture Item 1 is a small hard plastic line coming out from the firewall along with a bunch of factory-wrapped wires. I think that this is the vacuum supply to the controls in the cab.
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Item 2 is a solenoid or relay or something with a two-wire plug on one side and a vacuum line coming out of the other end, I don’t have a clue as to where this would go or what it does.
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Item 3 is a vacuum line coming from a vacuum canister mounted on the far driver’s side and is a ball shaped canister. There is a vacuum line running from this ball to a tee that is opened on the other two ends. I think that one side of the open tee goes to the vacuum tap on the manifold and the other end of the open tee to Item 1, the line that runs into the cab.
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What’cha think???

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December 20th, 2005, 8:14 PM

MudHawg

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(Pic) Heater hoses and control vac lines

The VIN is 1G8EK18H4FF*****
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The GVWR as listed on the door jam 6100/2767
The GAWR is 3550/1610
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The engine has just been rebuilt and is a 350 out of a 1971 <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com

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I just measured the outlets on the radiator (3/4") and intake (5/8") and I will hook them up to the same size outlets on the heater core.
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I connected Item 1 to the manifold vacuum tap and the cab controls work fine. I am going to tie in Item 3 so it will run from the manifold vacuum tap to a tee, one side goes to the canister, and the other side goes inside the cab for the controls.
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Item 2 eludes me. The wire colors are solid brown and solid yellow. Some kind of trip for when a certain vacuum is reached? Maybe a trip for some transmission function? How about a signal for the ECM? Hook it up to a vacuum source and see what happens? I am sifting through some wiring diagrams now, but with no luck so far…
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>When I swapped motors, the only wiring that I hooked up was the electric choke and the hot for the dizzy from the ignition switch. I don’t know what kind of ramifications would result from excluding whatever brain or emission control systems the ‘85 305 had.

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April 28th, 2006, 11:51 AM

5.7Lblazer

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RE: (Pic) Heater hoses and control vac lines

cool another blazer with a 350 in it wut kind of carb. and intake manifold
is on it i kno it aint about wut ur talking bout
ijuss wanna kno

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April 28th, 2006, 2:14 PM

Nomad76lj

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RE: (Pic) Heater hoses and control vac lines

the one thing i can ancer for sure is that the top line from the rad to the core is the inlet and the other is the outlet . sorry thats all i can help you with for now.

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September 28th, 2006, 3:45 PM

MADDOGG_86_K5

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RE: (Pic) Heater hoses and control vac lines

THE UPPER LINE WILL RUN TO YOUR INTAKE MANIFOLD AND THE OTHER GOES TO THE RADIATOR. THE LINE COMING OUT THE FIREWALL IS THE SUPPLY LINE THE THE CONTROLS INSIDE. WITH OUT IT HOOKED UP YOU WON'T HAVE DEFROST FOR YOUR WINDSHIELD OR BE ABLE TO CHANGE TO THE FLOOR OR DASH VENTS. I HAD THE SAME PROBLEM WHEN I SWAPPED THE NEW ENGINE INTO MY 86 K5. YOU DON'T HAVE TO REALLY WORRY ABOUT ELIMINATING A COMPUTER AND HAVING PROBLEM BECAUSE IT DOESN'T CONTROL MUCH ON THAT OLD OF A TRUCK. I ELIMINATED MINE AND HAD NO PROBLEMS. JUST MAKE SURE THE SIGNAL WIRES FROM YOUR PICKUP COIL ARE PLUGGED INTO THE CAP AND YOU SHOUL BE FINE.