DanielC Posted June 4, 2018 Report Share Posted June 4, 2018 The L-20-B on the right has been bolted into the engine compartment of the white truck it was sitting in the bed of in this picture.This is an engine out of a 720 pickup,that had air conditioning.After putting the fan on the waterpump clutch assembly, I slid the radiator into the engine compartment. The fan is way too close to the radiator, it touches the radiator. The fan is bolted on backwards, because it sits even farther forward bolted on the correct way.I removed the waterpump clutch assembly, and put the fan back on the assembly, and set it fan down on a bench. This is the height from the mounting surface of the waterpump to the fan front edge, about 4 3/4 inches.This is a fan from another L-20-B with a L-16 pulley, and waterpump, no clutch. It is a little over 3 5/8 inches. But the vanes on the L-16 waterpump are not as tall as the vanes on the L-20-B waterpump, or it would have been on the engine by now.What waterpump do I need to get that has no clutch, and taller L-20-B vanes? Quote Link to comment
banzai510(hainz) Posted June 4, 2018 Report Share Posted June 4, 2018 I would run the 510 stuff. The taller vanes? Does this matter? Most time the stat is closed anyways and is just cavitation around there. Ones the stat open its flowing But Im not a expert on this one I try to run the Atsugi stock OEM pumps Quote Link to comment
Ranman72 Posted June 4, 2018 Report Share Posted June 4, 2018 i ran a stock 510 pump on an l20b no issues been working fine in both your pics we cant see the veins the water pump i used i had to press the veins onto the shaft the rest of the way the factory left it a bit shy 1 Quote Link to comment
john510 Posted June 4, 2018 Report Share Posted June 4, 2018 I also use a stock L-16 water pump,no clutch fan and have no problems. Quote Link to comment
DanielC Posted June 5, 2018 Author Report Share Posted June 5, 2018 I quick update. I used the shorter L-16 water pump on the engine, with a non clutch fan from a second 1980 720 non air conditioning truck that was in the junkyard when I got the L20 that is in my 521 truck now. Thanks all for the suggestions. Quote Link to comment
datzenmike Posted June 5, 2018 Report Share Posted June 5, 2018 Most fans, specially at highway speeds and air flow, tend to move way more air that is needed, so fluid coupled clutch fans were used to limit fan speed to about 1,500-1,800 RPMs. They have a thermostat inside that allows more fluid to circulate and decrease the slip if overheating and the fan speeds up to 2,300RPM. This saves a little gas and reduces noise but the fan is being driven all the time including for the first 5-10 min of warm up and on the highway where vehicle speed forces air through the rad. An electric fan is even better and only on when needed. Quote Link to comment
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