Water Ports

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Coolant passages are below the intake ports in some A-series Cylinder Heads. They can be large holes or small holes.

Overview

Water ports keep the bottom of the manifold plenum at a hotspot for complete air/fuel burning, even at low throttle.

• A12GX has Four Large coolant holes, one beneath each inlet

  Album 4441

• Other heads have either no coolant holes, small ones, or a mix:

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• Standard Datsun 1200 heads have no coolant holes on the intake side.

Water outlet
Album 14473 Album 11093

Interchange

A-series heads will interchange with either dry or wet Intake Manifold with the following caveats:

• If the intake doesn't have coolant passages, tap the head's coolant ports and install plugs

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• If the intake has coolant ports, but the head doesn't, it may bolt on without modifications. Idle and low-throttle running may suffer due to insufficient heat. However, heavy throttle operation should be OK.

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Port Plugging

Two methods
* drill, tap and fit plugs
or
* use RTV sealant plugs 

Discussion: H89 water gallery pluging?

Screw-in Plugs

Directions for plugging the cylinder head with blind plugs:
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Nissan plug parts
99996-H1149 STUD & PLUG KIT 

You can buy grub screws in many places, most auto shops for example. Measure the hole, tap the mext mm up and screw in a plug. A bit of form-a-gasket, copper seal or anti-seize on the threads will help prevent corrosion and seizing.

Nissan Competition head 99996-H1165

RTV Plugs

If your dry inlet manifold comes down far enough to cover the holes, you can use silicone sealer like this:
Album 23478
This is an easy way to seal it, but coolant may leak when you change the manifold. Just re-seal it each time. By contrast, blind plugs are a one-time semi-permanent solution.

Used RTV silicone sealer. After fitting the intake/exhaust gasket, before fitting the intake manifold, press some RTV into the water ports, the put a button of goo over it. Let it tack up slightly before fitting the intake.

Album 4848