Bus heater plumbing

23Hourston

23Hourston

Well-Known Member
So going to throw a bus heater in the ol 23 Hourston sbc 350. Heater under rear table seat. A couple questions
.. I have a couple 3/4 ball valves to shut off supply and return and have 5/8 barb fittings in the water pump and manifold.. Problem.. I can't find a reducer to fit the 3/4 shut offs and 5/8 hose. And even if I did. That's I a lot of potential leaks with all the extra fittings . Which brings up the point that. Correct me if I am wrong. That the water pump and manifold have to be looped. And not closed off. Maybe shutting them off temporary is ok ?
Part 2
To get the heated air out of the rear seat box I want to use 3 inch pvc plumbing pipe. Might even have a run of it going into V berth and up to dash nicely hidden for defrost..
The short of it...
...Pvc can handle the heat?
...How to make heater hose with as few connections as possable.
Long post I know.
Mid to high end diesel heaters are not in the budget.
 
I have seen a few times (trucks, tractors, ect) where there is a loop from the water pump to manifold with no restrictions and a valve between the supply and return as a short cut. When the valve is closed all the coolant is forced to flow through the heater core, as the valve is opened more and more coolant takes the short cut to the manifold. The heater cores were always warm and in summer we would often use a double barb fitting to eliminate the heater core but at >45C every BTU you can exclude from a sun baked metal box the better (probably less of an issue on the water).
 
Blocking off the coolant flow to the heater would be the same as not having the heater there so yes you can put a temperature control valve in. You only need one valve unless you want two valves at the engine in case of leak.
If you want a temperature control I would mount one valve close to the heater somewhere easily accessible. You can even get cable operated coolant valves.

PVC is fine for the air flow, just remember air needs to get into the heater compartment also..

Diverting some coolant flow back to inlet side of engine would actually raise the operating temperature of the engine as the intake manifold hot coolant pressure would be fed into the cool suction side of the water pump bypassing the heat exchanger.
 
Wild Bill said:
Blocking off the coolant flow to the heater would be the same as not having the heater there so yes you can put a temperature control valve in. You only need one valve unless you want two valves at the engine in case of leak.
If you want a temperature control I would mount one valve close to the heater somewhere easily accessible. You can even get cable operated coolant valves.

PVC is fine for the air flow, just remember air needs to get into the heater compartment also..

Diverting some coolant flow back to inlet side of engine would actually raise the operating temperature of the engine as the intake manifold hot coolant pressure would be fed into the cool suction side of the water pump bypassing the heat exchanger.
Click to expand...

Thanks for the info
 
Fan speed will take care of the amount of heat you need. I have one that usually gets run on high all the time
I have two shut off valves in case of a rupture but it stays open all the time basically

You could put in 3 valves in an h pattern , two shut offs and a bypass... if you really wanted...
IMO just get the correct sized valves.
 
Fixit said:
Fan speed will take care of the amount of heat you need. I have one that usually gets run on high all the time
I have two shut off valves in case of a rupture but it stays open all the time basically

You could put in 3 valves in an h pattern , two shut offs and a bypass... if you really wanted...
IMO just get the correct sized valves.
Click to expand...

Installing a bypass like suggested with a third valve in a h pattern will just increase your engine operating temperature.
 
Wild Bill said:
Installing a bypass like suggested with a third valve in a h pattern will just increase your engine operating temperature.
Click to expand...
a good point, but i do not believe any engine manufacture designed the cooling system dependant of a bus heater for cooling?
 
All I'm saying is the manufacture didn't run a hose from the intake manifold (which is the hot side of the engine) to the water pump, (the cool side of the engine). It effectively removes the radiator or heat exchanger from the system.
You don't need or want an additional bypass, (the manufacturer has already designed one into the engine).
Just run the coolant through the heater.
 
all the manufacturer's have a thermostat bypass to promote flow through the engine and shorten warm-up time till the thermostat opens and directs flow to the heat exchanger
 
Wild Bill said:
All I'm saying is the manufacture didn't run a hose from the intake manifold (which is the hot side of the engine) to the water pump, (the cool side of the engine). It effectively removes the radiator or heat exchanger from the system.
You don't need or want an additional bypass, (the manufacturer has already designed one into the engine).
Just run the coolant through the heater.
Click to expand...

thats exactly what mercruiser does on my 2008 350 mpi mag. intake manifold to water pump. i removed that hose and ran 5/8" hose to heater core and back. only complaint is that idle i dont get much heat. 12-1400rpm it pumps out a lot
 
Fixit said:
thats exactly what mercruiser does on my 2008 350 mpi mag. intake manifold to water pump. i removed that hose and ran 5/8" hose to heater core and back. only complaint is that idle i dont get much heat. 12-1400rpm it pumps out a lot
Click to expand...


change the stat?
 
it worked in an inboard i used to have..
 
Fixit said:
the engine runs at 165 all day long, its just an issue of not enough flow at idle.
Click to expand...

I agree. We ran circulation pumps on school busses. Using one might pull the engine temp down lower than 165 though.
Nothing wrong with a hotter thermostat, typically less engine wear and often better economy.
Insulating hot side heater hose with foam plumbers insulation can help reduce temperature drop at the heater, often pretty long runs.
 
Well I went to see what my stat range is. And the hose ain't going to be reusable once it comes off.
Then I remembered having a hell of a time finding that hose to begin with. Took trial and error and sacrificed a few hoses till I got it right.
Anybody knows the part number for it
Chev 35020170311_170922.jpg San Juan engineering cooler
 
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