Salesguy, I'm not saying timing is the cause of your problems, but eliminating it as the cause may help you. We all tap other's first hand experiences for information and that information may lead us to an answer to our own problem. May not. All the other replies you've received may be on the correct track and mine not.
In my case I had an overheating problem at idle, once I got out on the road it ran at what I thought was an acceptable temperature. When I got back to my garage, idling , it once again overheated. I have my total timing [initial plus mechanical] set to 28 degrees. Twenty eight is the setting I obtained best power and torque with on an engine dyno. My mechanical advance is 9-10 max. At idle the nine degrees of initial timing was too low. The fuel air charge was burning as it went through the exhaust port rather than in the combustion chamber. No, I can't prove that but that's what I surmise after a few years of experience with engines. My vacuum advance can has a range of 20 degrees. The hose from the vacuum advance can on the distributor was connected to the stepped vacuum source on the carburetor. The stepped port connects to vacuum source above the throttle plates, low vacuum at idle. I relocated the hose from the stepped port to the manifold port. The manifold port connects to vacuum source below the throttle plates and has full manifold vacuum at idle. Before I changed the location of the vacuum source my distributor had nine degrees advance at idle, after I changed the vacuum source my distributor had the initial nine degrees plus twenty degrees vacuum for an idle advance of 29 degrees. After adjusting the carburetor to compensate for the increase in timing my engine runs at 600 RPM idle at an acceptable water temperature.
Of course this may have nothing to do with your problem but the info is there if you can or want to use it.
That is for my engine and may not be the same with yours or anyone elses but it may give you a path to follow if all others fail in your quest to solve your overheating dilemma. Al
