Dear Dave

I suggest that it is the pump.  If you can get a flow meter that will really

help.

 

I would bet the pump is cavatating at the highter RPM.  Without the

thermostat it cant build pressure to over come the cavatation te

 

I don’t think so.  I ran the 20B up to 7000 rpm on the dyno with no thermostat.  Flow rate continued up with the rpm – no problem.

 

Al