If you can get a plug for the back of the head, then all you need is a 120Y lower radiator hose.The later A series engines had the heater take off on the pipe going into the engine, so the metal sleeve in the middle of the hose wasn't needed.Makes for a much neater installation.
I've driven (raced) cars in summer with the heater turned on & it doesn't make much difference to the temperature in the cabin, because you're hot already.Usually at that stage I admit defeat & get a larger radiator, usually a 3 core one.

On a bit of a tangent, I have my heater unit out of the car. Looking from the cabin side and just above the core there is a wire coil going to a 2 pin plug. My cars been in bits for so long I have no idea what it is or what its for. Any ideas.

Does anyone know what the thread is for the heater fitting at the back of the cylinder head?

You can get the plug from Nissan.

00931-30610 PLUG-HEATER OUTLET HOLE $1.42 USD




From the part number this is a taper thread. 10 mm long. Threads unknown.

Quote:

This is the 2-speed resistor:




See Heater Wiring. If you have any further questions, please create a new Topic for it.

I would not recommend blanking both the inlet and outlet on the engine or just looping them together (although I have in the past).

either method CAN cause problems.

what I suggest is looping them, but to fit a restrictor inside the hose with a 3-5mm hole.

this way you avoid air pockets and stop the coolant from taking the easiest path.

How can it cause problems? It was the factory setup.

If you have air pockets, that can cause problems -- even if you have the heater in place.

It is important to bleed the system after flushing or refilling the engine coolant. The burp method seems to work fine. Drive it to full temp, let it totally cool down, then top up.