Have a set of springs that came on my 306-2 heads,only specs that came with them is (good to .650 lift)????,never used them, and was wondering if anyone might have any idea as to what pressures these might have@open,closed,etc.would like to use them for another project. thanks, Jim

Just take them to your local machine shop and have them tested so you will know for sure. Indy will use different springs depending on what the head is being used for, so guessing at it is not the best way.