The Z that almost killed me

[Zed Head]

The port at the back right of the head is only for the heater core supply. It actually affects flow in a negative way when coolant flows out at that point. It's a necessary evil to keep the people in the cabin warm. Some other car models used what's called the block drain plug port, under the manifolds, as the source for heater core supply.

Here's a diagram of the coolant flow. Notice that the heater core supply is not even shown. Coolant flows through the block, up in to the head and forward to the thermostat housing, then out to the top of the radiator.

[Noah Scarpelli]

Thank you Zed Head. So much. So basically, i should really invest in restoring the coolant route to the originally planned and executed route that existed before someone decided to reroute it in a stupid way? Update : coolant is super oily and i do believe my head gasket went.

[Zed Head]

A blown head gasket will cause overheating. Check your radiator also, it may be plugged. How did the old water pump look? Were all of the blades intact? Does your fan clutch work? Maybe the overheating happened after you got off the freeway and did a lot of stop and go driving.

There are a variety of methods for checking if you have a blown head gasket. A cylinder pressure test might show you something, along with the appearance of the spark plugs and piston tops.

The missing thermostat is a sign that the engine had been overheating for a while. It's one of the thing people do when they don't understand the root cause of the overheating problem. One scenario is that overheating started from a bad water pump or radiator, leading to a blown head gasket, leading to more overheating after the common fixes were applied. You might have a warped head also, they don't like overheating.

[siteunseen]

You can get a loaner compression gauge at O'reillys or Advance Auto.

[Stanley]

Here's a BSPT plug for the outlet on the head.

McMaster-Carr

[Noah Scarpelli]

Stanley. should I plug that outlet? I puled the valve cover off and talked to my step father about how the engine looked after the over heating when i was going to the hospital and he said that there was coolant boiling out of where the intake manifold mounts to the head. So, now I'm in the process of replacing the head gaskets and other relater gaskets. Zed Head, the water pump seemed to be ok, but i''ll replace it anyway. I hope I can find a head if need be!

[Stanley]

You can plug it or hook up the heater. On the 240Z there's a Wye hose barb fitting screwed to the right side of the block that the return heater hose, the intake manifold heater hose, and the hose that returns coolant to the water inlet all attach to. Don't know if the 280 is the same.

What I did was put tapered rubber plugs in the hose barbs and clamp silicon caps over them. But if I lived in PA I'd want the heater hooked up.

[siteunseen]

You'll be a full blown mechanic after a successful head removal, http://www.classiczcars.com/forums/tech-pubs-howto/42420-77-280z-head-removal-%5Bstep-step-photos%5D.html

Good luck!