After Martket Thermostat Housing

Fine sandpaper and a flat surface, rub the stock, aftermarket, chrome plated housings in a gentle circular/figure 8 motion until you see a uniform flat surface, skim coat of ultra black on both side of a paper gasket, torque to specs, allow to cure fully before it sees any liquid and good to go. Never had a problem with my method. All in the prep and assembly. And you can repair a corroded or warped housing also this way, been there, done that.