What brand were the lifters?
What was used for assembly lube, the red "taco sauce" or moly paste?
Did any of the lifters go into their bores tight?
If I may offer a tip for future reference...during mock-up I always use a brake cylinder hone and lightly "kiss" the lifter bores to make sure there aren't any boogers or left-over varnish that can hang the lifters up in their bores and keep them from rotating during operation.
If the lifter can't spin it
will go flat.
Eric