Timing does matter in an engine that is overheating.
If it head gaskets or exhaust, you can find this easily by having the engine idling and fill the radiator to the top. Watch the coolant. Most times there will be a few bubbles from fillng, but they should stop. If you continue to get bubbles after a couple of minutes then you may have a head gasket or exhaust problem. Possibly a cracked head.
The 216's were prone to cracking heads.
