I use MLS Cometics on my hemi. I don't have any leaking with the gaskets. I coated both sides of the gasket with copper coat spray sealant before installation. I thought I had a leak between the gasket and the head or block once, but that turned out to be a leak where the intake seals against the block and head. I re-sealed the intake and it's been dry since. This is a common issue with Hemis. I also have aluminum heads on an iron block.