[Greg Marriott]

I do run an 85 deg C thermostat. The problem arises because the pick up from the rear of the inlet manifold comes into the thermostat housing after the thermostat, therefore when the thermostat is closed the coolant takes the path of least resistance down the -6 hose and consequently the coolant never gets hot enough to activate the thermostat in normal road driving.

On the track when the engine is working hard and operating temps are a lot higher the problem probably would not occur.

The ball valve in the line seemed to me to be the simplest fix and a way to accomodate all conditions.