I run with a 302 and the pressure cap is rated at 13 psi. Approximately 14 litres - 50/50 water/normal antifreeze. Fortunately since I have had the 40 not experienced any overheating problems (yet) although it has got close sometimes. Never forget our trip to Le Mans Classic way back in 2010. Incredibly hot with temperatures at times pushing the upper 30 degrees C. This was during the day AND night. Ian Anderson - you will remember that trip and the track session Friday evening. As Frank says best get the rear head bleeds. Pair subsequently fitted on my engine with help from Frank so to avoid localised overheating.