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help please i think i have done everything.....chev 327 small block ..I had an overheating problem and did the following...1 replaced the radiator with a double core as used by the cobra guys here in south Africa...still overheated...2. removed the thermostat still overheated....3. checked all of the hoses... found one of the hoses (spiral chrome ) had some plastic liner which had come loose and was inhibiting the water flow... 4. changed that pipe......ran the motor without thermostat and no more overheating..... replaced the thermostat 160 deg and the heat gauge goes to 210 then drops back to an acceptable level and stays there... why does this over heat cycle happen... the temp gauge sensor is in the cylinder head (cast iron) intake manifold is aluminum which houses the thermostat..checked the fan belt it is good and tight

Could be a air pocket in the head, try moving the sensor to the intake if you want to. Now if I were you, as long as it comes back down to 160, I would say "problem solved" and go on and worry about something else. Is it hot down there, it sure is in the Midwest of America.

It sounds like the motor is heat cycling like it is supposed to. Taking the temp from the head will give you higher readings than what the thermostat will see. thus the cycling from 160 to 210. You can drill a small pilot hole in the thermostat to pull a little water up to the thermostat to even out the temp swings. Try a 1/16th inch hole and go from there.

Keith...