Hey ed, I used a guage and cranked it to get my compression figures. I used the compressor to see if it would pressurise the radiator when compressing the air in each cylinder. I used hylomar spray on the gasket when installing it. What I think is that between the two ends of the orings there might be a small gap, could that be the reason why its blowing into the water jackets? If I do go for a HKS MHG do I have to put the orings back in or what would you do in this case? Cheers