Correct Heater House Routing - Vortec 350

[Portland68]

Having trouble determining the right solution for cooling my motor and want to check I have it right before I start driving the truck. It is a 72 k1500 with a Vortec 350 in it.

How/where exactly are my heater hoses supposed to be routed and do I need a bypass?

Currently the top of the water pump and front of the intake manifold are plugged and I have a hose going off the passenger side of the water pump to the heater core and a hose going from the heater core to the radiator.

Through some looking into things on this site it seems I may need to run a bypass from the top of the water pump to the front of the intake manifold but i also saw mention of running a line to the block on the passenger side.

Any help would be appreciated, I am running a Stant 45358 thermostat.

[FirstOwner69]

We had a discussion a couple days ago about heater hose routing differences for different years. Based on that, your hose routing sounds correct for a '72.
https://67-72chevytrucks.com/vboard/...d.php?t=794821

I have a Vortec GM crate engine and was told by GM to run a bypass since old style heads had a provision for an internal bypass, but Vortecs didn't. Here's a picture of what I did with my '69. Your intake may be different.

[Portland68]

That’s the thread that got me looking into what I needed to do, thanks for your reply. Looking back I think my engine builder mentioned something about it in one of our early conversations and that may be why he left the passenger side opening on the block unplugged - so I should be fine to keep that plugged and run a hose from the intake manifold to the top of the water pump?

[geezer#99]

Any ports on the pump are inlets, not outlets.
You need a bypass like in the pic.
You need a hose from the intake to the bottom of heater core and a return hose from top of core back to either the water pump or to the rad.

[Portland68]

Alright the plan is to put the temperature sending unit in the driver's side hole, the heater core inlet in the passenger side hole, the heater core return to the water pump, and the external bypass from the 3/8 NPT fitting at the front of the intake to the 3/4 NPT fitting on top of the water pump - this should provide adequate cooling until the thermostat opens, correct?

Thank you all for your replies

[geezer#99]

You got it!
It’s not for cooling it’s for flow.
Vortec heads need good flow thru them so no hot pockets are created that might crack the heads.

[FirstOwner69]

Originally Posted by Portland68

Alright the plan is to put the temperature sending unit in the driver's side hole, the heater core inlet in the passenger side hole, the heater core return to the water pump, and the external bypass from the 3/8 NPT fitting at the front of the intake to the 3/4 NPT fitting on top of the water pump - this should provide adequate cooling until the thermostat opens, correct?

Thank you all for your replies

You've lost me somewhat on which holes you are referring to.

By "...the driver's side hole..." do you mean the one in the driver's side head between cylinders 1 and 3? (See circle in picture below) The consensus here is that it's the best location for the temperature sensor. If so, the sensor will need to be turned down from 1/2"NPT to 3/8" NPT. Forum member Brian Mac did mine. I've read that A1971Blazer also does it.

I'm not sure why you'd run the heater core return to the intake rather than the radiator nipple which appears to be correct for a '72. However, the hole on the passenger's side of the intake will certainly work.

Also, note that in the picture in post 2 that I needed a spacer under the water neck to clear the bypass fitting. Probably depends on your intake though.

[Portland68]

Originally Posted by FirstOwner69

You've lost me somewhat on which holes you are referring to.

By "...the driver's side hole..." do you mean the one in the driver's side head between cylinders 1 and 3? (See circle in picture below) The consensus here is that it's the best location for the temperature sensor. If so, the sensor will need to be turned down from 1/2"NPT to 3/8" NPT. Forum member Brian Mac did mine. I've read that A1971Blazer also does it.

I'm not sure why you'd run the heater core return to the intake rather than the radiator nipple which appears to be correct for a '72. However, the hole on the passenger's side of the intake will certainly work.

Also, note that in the picture in post 2 that I needed a spacer under the water neck to clear the bypass fitting. Probably depends on your intake though.

Ahh sorry for not being specific I'm running the Edelbrock 7116 intake manifold and there is a hole on each side of where the thermostat housing goes, my plan is to run the temperature sensor to the hole on the driver's side (which should be fine although the location you mentioned is preferred).

I guess it doesn't really matter to me how things are routed as long as I am getting the right cooling - are you saying my hoses should be heater core return to radiator and heater core to water pump with nothing except my external bypass going to/from the intake to the water pump?

Sorry for all the questions my dad and I have never done a Vortec before!

[FirstOwner69]

Originally Posted by Portland68

I guess it doesn't really matter to me how things are routed as long as I am getting the right cooling - are you saying my hoses should be heater core return to radiator and heater core to water pump with nothing except my external bypass going to/from the intake to the water pump?

That's just the option that would be consistent with what seems to be the norm for '72s. My '69 goes from the core to the intake (the '69 norm) and has always worked fine.

I'm just being a bit anal in case originality is important.

Jim

[Portland68]

That's fair, hopefully the Vortec works out otherwise I'll definitely be wishing I kept it original for my rebuild. Sounds like I will be running a bypass similar to your set up but out of the 3/8 fitting on the front of the intake manifold so I don't have to machine down the temperature sensor, and then intake-core for the heater core inlet and core-water pump for the return (or core-radiator for the correct look) Thank you Jim!

[FirstOwner69]

You'll like the Vortec.
If you do decide to have the sensor turned down, I think Brian Mac only charged $20 in 2011.

Jim

[Big Kev-O]

I used a small "H" adapter on the lines running to my heater core and installed the sensor in the intake manifold. Works great.

[garyd1961]

All you need is a hose going from the intake to the heater core and back to the water pump (not the radiator).Unless you have ac then you will need another type bypass like in Firstowner69's picture.

[54blackhornet]

Can you explain the H fitting ?

[Bigdav160]

Originally Posted by 54blackhornet

Can you explain the H fitting ?

Looks like it lets water exit the head/intake and return to the water pump.

A bypass is needed to keep water flowing when the thermostat is closed. Not needed once the thermostat is open.