[SDGoat619]

What t-stat should I use in my 455, 180 or 195. I have heard and read in many places that people use both. The motor is in a 65 lemans and I believe the radiator is stock but I am not positive.

Thanks as always for the feed back

[David Jones]

How do you drive it?
Just a little?
Daily driver?
Assuming that your cooling system has enough capacity to keep the engine at the rated temp given the way your 455 is tuned.
I tend to drive mine enough to get the OIL up to operating temp when I drive it. I run a 180.
If I didn't really drive it like that I think I'd run the 195, hoping to hold more heat so maybe the moisture that can build in the oil might burn off better.
You're in a fairly steady warm area so I might lean toward a 180.

I believe Mother GM used a 195.

Bottom line? Make yourself happy........

If the tune is wrong the thermostat ain't magic, it can't fix a timing issue or a lean carb.

[68 Firebird]

I went with the 180 after trying the 160. Engine seems happier at temp of
180-190.

[Joel Koontz]

If have a low compression engine that will never ping, no matter how it is tuned, or how you drive it, you probably want a higher temp thermostat. The higher temp (assuming it does not require detuning, etc.) will make the engine slightly more efficient.

If you have a high compression engine that pings unless it is perfectly tuned, you may want a cooler thermostat. "All things being equal" the cooler engine will be less prone to pinging and should allow you to tune for slightly more power.

There are a lot of factors that come into play, but IMO the engines propensity to ping would probably be the most significant factor in determining which would be best.

[goatwgn]

Originally Posted by 68 Firebird

I went with the 180 after trying the 160. Engine seems happier at temp of
180-190.

I did this as well. Mine runs smoother with the 180 thermostat. I also drilled 2 1/8 inch holes in it to keep the air bubbles out.

[johnsma22]

The thermostat only sets the minimum operating temperature. The temp at which your motor ultimately operates will be determined by a number of factors, like state of tune, etc., and the ability of your cooling system to shed heat. If your cooling system is not capable of bringing the coolant temp down to 160 degrees, it will not matter if you have a 160 t-stat in there.

Just an FYI. There are two basic types of thermostats currently available: You have the balanced sleeve thermostat, and the reverse poppet thermostat. Both types function in the same manner, but have distinct differences. The reverse poppet thermostat opens against the flow of coolant from the water pump. The coolant, being under water pump pressure, is used to help the reverse poppet thermostat stay closed when it is cool so as to prevent leakage.

The balanced sleeve thermostat allows pressurized coolant to circulate around all of it's moving parts, and equalizes the system pressures above and below the thermostat’s moving valve. Therefore the thermostat is pressure balanced and will respond to system temperatures only. It provides a fast temperature response time and increased coolant flow to the radiator. For a performance engine application it is recommended to use the balanced sleeve design for it's added flow capabilities. See photo below:

I run a 180˚F Robert Shaw balanced sleeve T-stat.