Had a pull tractor head needing work that has 300#'s of valve seat pressure. Our hand spring compressor does not have the needed leverage and our air spring compressor didn't have enough grunt with the shops 150# line pressure. Solution was to fab a line from the nitrogen bottle we use to fill race car tires. The pressure was set at 150#s to start on each valve spring and then raised till retainer cleared keepers, <>340 #s. One does not START at 340 as this will knock head off bench. Moderator may move to Hipo or Tools. Did have to replace black O-rings in spring compressor with green high pressure ones used in a-c systems. May come in handy for someone and if not file it in your dictionary of useless facts.

Evan