It's the head gasket issue. I have a brand new Fel-Pro NOS set for an aluminum engine along with an entire aluminum engine and the car it came out of and the reason for filling that engine is to create a deck where there is none. They diecast that block and used iron liners that were captured by die cast aluminum and the gasket would weep and get to that aluminum with too many heat cycles that aluminum let go at the tops from the iron and began to chip away and fall off removing clamp surface and weeping by 50-70k miles. That's why they quit.
My grandfather ran the line for those at kokomo Chrysler. His head was covered in burn spots from pots exploding and popping. It was really early I. Die cast production. He went on to Mattel toys and cast the hot wheels n stuff like that after chrysler closed that operation down. He had also wanted move anyways to California and scuba dive and fish. He was a highly decorated Korean war vet. Purple heart, silver star, in 3 or books about the war and carried wounded, while wounded off the front line. I could hope to be maybe half of what my grandfather was. He also laid carpet...as I do. I got share stories with him as he gurgled pneumonia in his last weeks. He chuckled smiled. You would never known unless you heard his voice.
He was maybe 5 5" tall or so..
Great man and role model I miss very much.