[Healeys] Engine Temperature Info ??

[Oudesluys]

Old hands say not to remove the thermostat as it may disturb the flow in 
the engine causing uneven cooling.
The behaviour of your temperature gauge is perfectly normal and 
indicates that you have a fairly healthy radiator but it is working to 
the top of its capacity, as it was originally.  In heavy stop and go 
traffic the car will overheat.

These days there is a lot of stop and go traffic so you do need an 
electric fan controlled by a thermo switch to have sufficient cooling 
when stationary or slowly driving or driving in the mountains. Remember  
cars overheating along the road in the mountains in the 50's/60's and do 
you see any of that today? Reason: radiator with plenty of (over) 
capacity and high power electric fans in modern cars.

Nearly all heat generated by the engine has to be dissipated by the 
exhaust and the radiator, so be sure your radiator and water pump are 
tip top. Do not have the radiator rodded, waste of time and money. Have 
the core replaced by one with a larger cooling capacity. Also have a 
threaded plug hole (M20) fitted in the top to accept a thermo switch. 
There are hundreds of different thermo switches to choose from with a 
M20 thread.

I prefer my engines to run hot,
a) it runs more efficiently,
b) the radiator will tranfer more heat as the delta T is bigger.
I always installed a thermostatically controlled electric fan in my cars.
The engine temperature with a properly (over) dimensioned radiator is 
controlled by the engine thermostat only. For the Healey you need a 
sleeved thermostat to block of the bypass. You also need a high pressure 
radiator cap to raise the boiling point of the coolant. Do not go higher 
than 10 or may be 15psi. The thermo switch should switch on the fan at 
about 100C/212F and switch off around 5C over the opening temp of the 
thermostat if fitted in the top of the radiator / top radiator hose / 
top of thermostat housing. I also use an overflow tank  and an extra 
thin rubber seal in the radiator cap. The expelled coolant (because of 
expansion when hot) will be collected into the overflow tank and will be 
withdrawn into the radiator when the engine cools down. To be effective 
you have to fill up the radiator to the top of the filler neck.

Sleeved thermostats are available in various opening temperatures: 
68C/155F, 72C/162F, 80C/176F, 82C/180F, 86C/187F a.o.

For a AH100-3000 I would probably set it up with a sleeved thermostat of 
180F or 187F, with a thermo switch around  212F in and about 205F out. 
Adding a powerful multi-blade modern electric fan, not e.g. the pathetic 
early 4 blade affairs from Lucas. Pushing or pulling is not an issue but 
fit it as close to the radiator as possible, preferably directly to the 
core. Rad cap of 10psi. Use proper coolant to prevent corrosion and sludge.
Kees Oudesluijs
NL