I found it necessary to run the 6 banger and alloy a little hotter and fill from the bottom cavity to the top, reason being the camming action of those moulds has very little cutting power the closer to the handles you are and this is why so many seem to break when forced open. I keep my MAP gas near when casting just in case the alloy gets a bit cold. I shunned those 6 bangers for years and now I realise how silly I was or am depending on who you ask. The old 500 release agent was great so the new one must be from the gods. Regards Stephen