My suggestion would be to remove the line that goes from the back of your block to the front and plug both ends. It would mimic the OEM heater core when you’re not running heat in the car. Hopefully improving your cooling issue?

Can you point out which line and how should i plug it?

Edited December 22, 20213 yr by jalexquijano

On 12/21/2021 at 11:48 PM, Barefootdan said:

My suggestion would be to remove the line that goes from the back of your block to the front and plug both ends. It would mimic the OEM heater core when you’re not running heat in the car. Hopefully improving your cooling issue?

Can you point out what is your suggestion? My thermostat is rated 160 degrees so it should keep the car cool during stop and go traffic situations. 

I took this recent pictures for your reference.

On 12/22/2021 at 1:03 PM, jalexquijano said:

Can you point out which line and how should i plug it?

That's a 280Z above.

Here is the 240Z's...

 

10 hours ago, siteunseen said:

That's a 280Z above.

Here is the 240Z's...

 

Still dont see any comments regarding my pictures? 

Have you tried running your Z without a thermostat? They definitely have a purpose but you could try it. Don't get too far from home though in case it over heats on you.

Also you could try putting some kind of reducer in the hose coming off the head. It is possible the pump is pulling the coolant through too fast resulting in those black plugs you've shown us. 

It's a balancing act, not too fast but also not too slow. I still think you could put a thermometer in the radiator while the car is parked, no wind flowing besides the radiator fan and give us a temp reading. No "stuck in traffic" reading. Just sitting still in your garage.