I thought that this thread was trying to analyze how an engine will run with or without a heat crossover passage operable. What is the purpose of it and how will the engine be affected if it was blocked off. To make a proper comparison, you have to isolate and change only one variable at a time or your rusults will not show how that particular change affected the engine.
Trying to compare a 1975 engine to a 2001 engine is trying to compare apples to oranges. Too many variables to isolate how changing just one will affect the process. And why are you choosing 75 model year that had lots of emissions problems to affect the engines and how they ran. Try a 68 - 71 era engine and isolate the heat crossover and explain the affects the engine.
There was a couple of statements worded so that someone may get the wrong idea and I was just trying to make it clearer.
