Slide hammer is the way to do it. To answer CatsRock, you can never find the correct thermostat from any parts store...they always give you one for a Windsor and the copper hat is smaller which will cause all kinds of overheating. I used the aluminum one from Pantera Performance with great success on my Cleveland. The new hole is a little bit bigger than a pin hole.
So true, as with almost everything on the old clevelands, I went through the thermostat nightmare unknowingly untill someone pointed out the difference, luckily WCCC had the correct one. Same thing when I rebuilt the carb, now I pretty much bypass the local auto parts and go directly to the cougar / mustang / pantera shops. :smoke:
Def worth the 20 something bucks from WCCC. On a record hot day in Evansville, In at 108 degrees the car was driven a while. She never went over 200. Im so happy with this upgrade, get the wccc part and a 160 thermostat and your problems are cured!