Hi a trick motorcycle engines is ,if there is a piston is on the way down ,you take a piece of thick steel I would say 1/2" for your motor cut it out so that you can drill 5 holes in it 4 for head bolts one the middle .The middle hole gets a nut welded to the under side (piston side) I'm thinking 5/8 ? Place a piece of the flat steel on top of the piston (same thickness as the plate if possible)put your bolt in and put some pressure on it .This would be done after it's soaked a while with some of the other ideas here .
Paul
