In a message dated 3/25/2011 1:18:59 P.M. Eastern Daylight Time,=20 bbradburry@bellsouth.net writes:

Lynn= ,

What is the pu= rpose=20 of the restrictor in the system??

Bill=20 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=20 get coolant up to temperature like 155 to 160. So I tape over 1/3 of the= =20 radiator. Still no good. So I cut a notch out of the edge of a standard 16= 0=20 degree thermostat (the bypass hole is plugged. Still no good. The notch is= =20 passing enough coolant to over-cool the engine. The notch is to let air pa= ss=20 through to be dumped at the swirl pot. So I got out another 160 degree=20 thermostat, and drill three 1/8" holes in the rim to let air bubbles throu= gh. No=20 good. Three 1/8" holes is enough to over cool the engine. The thermostat= just=20 never opens. So I end up with another new thermostat with one 1/8" hole in= the=20 rim to let air through. This works fine but only under a load, so the 1/8"= hole=20 cools an idleing engine and the thermostat never opens. But that was the= best I=20 could do, and by the end of the pace lap the engine is at 160 degrees and= the=20 thermostat is open.

The restricter came about of observing the lower hose collapse on the= dyno.=20 Those hoses all have a spring wire in them to prevent just that. But my ho= se was=20 less the spring. So if you have a 14 pound cap that works, how can the hos= e=20 collapse?

And if it does, isn't the coolant boiling in that hose? Perhaps so.= Smarter=20 people than I told me always to run the thermostat (and the spring) and it= would=20 never happen. It was said that the restriction of the thermostat slowed th= e=20 coolant speed and reduced the low pressure on the suction side of the pump= .=20

So on the racer where a thermostat is not always used, I have a perma= nent=20 restricter TIGed into the outlet. It is 1/8" thick and has a sharp edged= 5/8"=20 hole in the center. Always installed even when the thermostat is=20 installed. There may be some slight advantage in that the pressure in the= block=20 would normally be higher than in the rest of the system. I have a Shrader= valve=20 in the make up tank so I can check pressure after a session, but I never= =20 measured the dynamic head in the block. The pump impeller may be protected= from=20 cavitation as well, but I don't know that for a fact either.

Lynn E. Hanover

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