I used MLS gaskets on my 416 stroker engine in my drag car, couldn't get them to seal, leaked antifreeze on both sides. Called the manufacturer, was told to re-torque them, which I did, no change. Talked to my engine machinist, he said he had many customers using them and had never had any problems. He also said that different alloys will cut differently, even using the same cutters. You could see the ridge marks on the gaskets when I pulled the heads. Went to Fel-Pro severe duty gaskets, have had no problems whatsoever.