Most thermostats I have found had a small poppet valve (1").I have seen the #6 napa recommended. It is 170 degree only. It has the large poppet valve and fits the Y. My ford #COAE-8575-B has a 1.3" opening. The #6 is 1.5". This should help flow when its open. I also obtained the applications that use this thermostat. It fits evil little cars. Hope this helps.

Kenny  Onalaska, Texas