This might be my opportunity to brag about the -4.
I think the RV-4 cools better than the other models except, maybe, the -3 which has similar cowling.
O-320, fixed Bernie Warnke wooden prop with the Landoll balancer. I invested a lot of time with my baffling to make sure everything was sealed as well as I could get it. The markings of the baffling material (which is black) on the inside of the cowl tell me the baffling is well-sealed. I pull my oil cooling off the back of the shroud behind cylinder #4 but with an air dam to direct most of the air around the cylinder, and cabin heat from behind cylinder #2. Full-throttle climb out to, as an example, 8,000, (3k AGL, by the way), running 50-100 ROP, I
might get into the mid to upper 300 range. Once at cruise, typically 2400/20 running 50 ROP (carburetor) CHT 280-320 with temps usually not over 300. Looking at my previous flight logs, upper 200's is typical.
There is a recent series of articles on engine cooling in Kitplanes magazine and stresses many factors including air entering the cowling (VERY well-designed intake by Vans), baffling and seals, and air exiting the cowling and taking the heat with it. I think this is one place that could possibly be improved by many builders. My oil temperatures are on the lower side, in the 180-200 range and that is with the oil cooler gate closed and the air intake partially blocked off, the amount depending on OAT.
Just some reference numbers from a well-designed cowling and paying a lot of attention to air flow over the cylinders. Can the engine be too cold? Yes, but that is usually not the problem. I do block some air entrance when Winter arrives.....
IMHO YMMV