If you wanted to run your engine a bit cooler, either to richen up the AFR or reduce engine knock due to heat, you went out and bought a custom thermostat at a cost of about $80 with shipping as I did not once but twice got ripped off by a vendor of Corvetteforum.

I did this to find a 178 custom stat only allowed a maximum of 163 at highway speeds when used with a race radiator !

I was upset at this cost and not getting what it was supposed to be so I began studying the thermostat design and with the experience and knowledge of teammate Gary S, I began testing a method of modifying the stock thermostat and found for less then few dollars I could make the stock thermosat adjustable.

Review the process at :

Save money and modify stock stat

Here is my style of cooking on the stove, testing each shims thickness to opening temp.



Thus for a few bucks you now can adjust your stock termostat at a lower opening temperature.

John,

This is a good idea anf I saw something like it before as it makes a world of difference.

I have a write up from somewhere showing a similar idea and his results were astounding.
I will search for it.

George

Here a little upgrade...
Adjustable Thermostat
Hope you like it!

Stefano

Yes I considered that but my fear was if anyone is doing such a mod and not done just right it could leak later on and/or suck air into system
Using a shim does not take more then a 1/2 to do the swap and using different thickness shims would dicate when stat begins to open

Also the newer stats function differently ( starting around 2002 model years on C5) and may also require some of the main spring to be cut down.