Originally Posted by Nova RV
Scott, I'm not questioning your analysis but how are lower CHTs bad unless they are so low the cylinders can't "expand" properly and not allow it to break in properly or cause increased wear? Lower temps within reason was always told to me as being a good or better thing.
My cut outs are similar to Keith's although slightly larger.
Yes, you can run too cool. However, I have no idea what is too cool on a lyc. There is a reason your water cooled engine has a thermostat. If your logic applied, a thermostat would not be necessary, just let it get as cool as it can. Automotive thermostats were put in place decades ago to keep temps up, not down.
Power is a function of heat. If the head is allowed to get too cool, you will unnecessarily lose combustion energy into the head instead of pushing the piston down. Engines are typically designed for an optimum level of heat loss through the head and ultimately optimum running head temps. There are other negative effects from running too cool, as well. CHTs are an indication of the balance between combustion temps, including combustion frequency and heat transfer from the head.
Ring seating has nothing to do with CHTs, nor does cylinder expansion. They are tied to cylinder wall temperature. The heads are aluminum and the cyl walls are steel. Very different heat diffusion rates. The cylinders also have different cooling fin design. I would not necessarily expect the barrel temps to follow a linear correlation with the heads and doubt that they do. However, I admittedly have no idea what the relationship looks like.