I just installed a 468 in my 70 Cutlass, replacing the original 350. The original rad has been replaced by an aluminum 4 core rad without a shroud. A 6 blade clutch fan has been installed. The engine was supplied without a thermostat and I was told it would not be required, I dont believe that to be the case. I havent run it too much but it doesnt seem to get hotter than 200 deg. in very hot weather. What thermostat should be installed for better cooling performance, that temp seems low?

Thanks

 

I prefer a 180 to get some cabin heat on cooler days. With that said a thermostat maintains the minimum operating temp and the cooling system itself maintains the max. 200* is not too low, but I would not call it high either. What fan set up are you running?

 

200 with no thermostat seems high to me. When I remove the stat from my engine the coolant stays around 140.

For better cooling performance I would recommend installing a shroud.

 

Kenneth is right.

And if you add any thermostat (even a 160°) it will restrict water flow, and you will have 200°+ temperatures. A thermostat will only set the minimum operating temperature; it does not control the maximum temperature.

To control the maximum, you must improve water flow, air flow, or both.

 

The opposite can be true too. With no thermostat the water can run thru so quickly that it doesn’t have ample time to dissipate the heat.
Make sure you have good flow at all temps and RPM’s.

 

I forgot about that, Mark.

The pump impeller can cavitate when the flow gets excessive. That leads to lower heat dissipation. In that case, a thermostat's restriction could lead to a lower temperature.