FellowTraveler
Well-Known Member
I've noticed most of the replacement thermostats on the 4/6bt are not "hi-flow" and look like the 6.2/6.5 bypass type thermostats with a somewhat smaller opening for coolant flow. I run the "hi-flow" in my 6bt which looks like the thermostats on the dual thermostat 6.5td but with a bypass valve on the bottom too.
I'm suspect of the smaller thermostats actual opening size creates an a pressure issue in the cooling system and question as to whether or not they actually do contribute to the system pressure rise at upper rpm's which everyone claims pop casing plugs (aka: freeze plugs) on the blocks of the 4/6bt series...
I bring this up because more than a few vendors have tried selling me billet covers to replace the plugs....
I'm suspect of the smaller thermostats actual opening size creates an a pressure issue in the cooling system and question as to whether or not they actually do contribute to the system pressure rise at upper rpm's which everyone claims pop casing plugs (aka: freeze plugs) on the blocks of the 4/6bt series...
I bring this up because more than a few vendors have tried selling me billet covers to replace the plugs....