Thank you for all the replies. I think I will check the spring and back flush the cooler. The baffling looks ok but I will try to seal a bit more. The reason I was more concerned at this point, is that at the end of August I am taking the RV6 to S France for two weeks, where currently it is +30c !! There are no cowl flaps and the inlet at the front is quite small compared to a Piper or Cessna.
In respect of the comments about the Lycoming 0-360. I also always thought this was one of the toughest versions. We used to have a Comanche 260 with the IO-540, which I believe has the same cylinders apart from the injection ports and of course 6 rather than 4 cylinders. We never had any problems apart from usual wear and in fact the bottom end had done 3300 hours on the original engine when we sold it.