Lynn,

What is the purpose of the restrictor in the system??

 

Bill B

You were not supposed to notice that or the thermostat.

 

 

When racing in cool weather or early in the morning, it is impossible to get coolant up to temperature like 155 to 160. So I tape over 1/3 of the radiator. Still no good. So I cut a notch out of the edge of a standard 160 degree thermostat (the bypass hole is plugged. Still no good. The notch is passing enough coolant to over-cool the engine. The notch is to let air pass through to be dumped at the swirl pot. So I got out another 160 degree thermostat, and drill three 1/8" holes in the rim to let air bubbles through. No good. Three 1/8" holes is enough to over cool the engine. The thermostat just never opens. So I end up with another new thermostat with one 1/8" hole in the rim to let air through. This works fine but only under a load, so the 1/8" hole cools an idleing engine and the thermostat never opens. But that was the best I could do, and by the end of the pace lap the engine is at 160 degrees and the thermostat is open.  

 

The restricter came about of observing the lower hose collapse on the dyno. Those hoses all have a spring wire in them to prevent just that. But my hose was less the spring. So if you have a 14 pound cap that works, how can the hose collapse?

 

And if it does, isn't the coolant boiling in that hose? Perhaps so. Smarter people than I told me always to run the thermostat (and the spring) and it would never happen. It was said that the restriction of the thermostat slowed the coolant speed and reduced the low pressure on the suction side of the pump.

 

So on the racer where a thermostat is not always used, I have a permanent restricter TIGed into the outlet. It is 1/8" thick and has a sharp edged 5/8" hole in the center.  Always installed even when the thermostat is installed. There may be some slight advantage in that the pressure in the block would normally be higher than in the rest of the system. I have a Shrader valve in the make up tank so I can check pressure after a session, but I never measured the dynamic head in the block. The pump impeller may be protected from cavitation as well, but I don't know that for a fact either. 

 

Lynn E. Hanover