You should have your initial distributor timing set on some type of machine…whether it’s a KR WILSON fixture, Sun machine or other. Any movement concerning your timing mark on your distributor is purely a guess on your part. I believe your timing should be advanced if you are having a cooling issue, but again you will be guessing.
There are seven indentation marks on the crab distributor adjustment plate. The mid-point is stock and is 4° advanced. The spacing of the marks is 2° each.
This shows my distributor set at 6° advanced. I now run with 7°.
Too much retarded will cause the engine to run hotter.