Heater issue

[jondee86]

OK. I figure that regardless of the thermostat setup, there will have to
be a bypass somewhere inside that block, otherwise you would have no
circulation when the thermostst was closed. I will also assume that the
thermostat is blocking the return from the radiator until it starts to open.

On this basis, where the hot water exits the head can be considered a
a good place to tap for the heater flow. The blockoff plate on the side of
the head at the rear would be just as good. And where the water exits
the head and enters the pump can be considered a good place to tap for
the heater return connection. If you are using the factory alloy pipework
you should be able weld/thread/glue a 5/8" barb for a heater hose.

The heater core will basically be running in parallel with the radiator, and
will be a bypass around the thermostat when the heater valve is open.
This may delay the opening of the thermostat slightly, but given the
difference in flow rates between the heater core and the radiator, I can't
see it having any significant effect on the engine warmup.

Cheers... jondee86

PS: Looking at your drawing, if the heater flow tapping is reasonably
close to the head, then you would only need to change the return hose.