| I've been working on assembly of Dee Ridgeway's built SGP engine for his "DEMONZ" and have come across something interesting in the cooling system. The Parts:
 I'm sure all of the parts above you are familiar with but I wanted to show something a little more that you might not be aware of. The thermostat has two valves in it, not just one. There is the main valve face that is ~1.75" diameter which controls the flow of coolant coming into the pump from the cool side of the radiator. But there is an additional valve at the back of the thermostat which is used to control the volume of recirculated coolant. When the engine is cold, the thermostat's main valve is closed but the recirculation valve is fully open. This recirculates coolant through the engine until it warms up to normal temps - this speeds up the warmup period. When the system is under heavy loads and producing a lot of heat, the thermostat will react to fully open the primary valve while at the same time close off the recirculation port. However, the way the thermostat housing is designed, you will never fully close off the recirculation port. This means that there will always be some volume of very hot coolant recirculating back into the block rather than only cooled liquid from the radiator entering the engine. Here's a look at the assembly:
 
The upper coolant pipe has three ports: two that go into the front of the cylinder heads where the hot liquid exits the engine and the third center port is the recirculation port. The lower coolant pipe connects to the outlet of the radiator and this is where cooled liquid is drawn into the pump. Inside of the housing shows you the ports: 
The large round opening is where the thermostat fits into the housing. The smaller opening within the housing with the square notch at the top is the recirculation port. The port below it that is somewhat crescent shaped is the heater core port. I dont know what the reasoning was when Nissan designed this housing, but it baffles me as to why they made the recirculation port the way they did. Even when the thermostat is completely open, thereby closing off the recirculation port, the recirc port is never fully closed off. Given the area that is opened when the thermostat is fully open, I see no possibility of the OEM pump cavitating, much less having that notch actually preventing it. Here's two shots of the thermostat in different positions: 
So the mod was actually really simple. Cut out a piece of sheetmetal to act as a blockoff when the thermostat is fully open and connect it to the recirculation valve of the thermostat. 
I dont have a thermostat in my engine since I am using an electric water pump and built a thermatic controller for it, but I have entirely blocked off the center recirculation port of the top coolant pipe with some thin aluminum sheet I cut out. I dont have any cooling issues with my vehicle even with electric fans and running the piss out of it on the track or street. Without having tested this new mod I can't say how much of a difference it is going to make. But, given that there is always hot water going right back into the pump at all times raises some concerns, especially when 95% of the hardcore drivers complain of their cars overheating in track events. Are all engine cooling systems designed to allow a recirculation port of this size to always be open even with the engine reaching critical temperature levels? This is such an easy mod to do - hopefully some others will take it on as well to see...
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Cooling System Mod >>>> - 
