Temps climbing in 318

Let me tell you my interesting experience. Sometime ago, OldmanMopar had posted that he believes that something (thermal cycling, ??) sometimes causes the fins to crack loose from the tubes. What this would do is to still allow great water flow, but reduce heat transfer

My 360, and later, a 318, with the original 273 67 2 core, did EXACTLY as yours. I had junked a /6 73--74 which ALSO had a 2 core in unknown condition, with the later style tanks.

I switched them, and the result was DRAMATIC. By the way, a rad shop told me my original 67 flowed plenty of water, and was clean. He told me it should cool a stock 360 "no problem."

I believe, that at least in my case, loose fins on tubes was the problem.

"Some day" I'll try and set up a test between the two.