Hughes has some of the most aggressive lobes available and I've known of engines that they simply could not be made to work in using factory lifter bores. The problem is not every block is machined that well. The lifter bores may not be positioned properly or they may have wear that allows the lifter to "tip" slightly and break the oil wedge. Did you measure the lifter bores and the lifters? Did you verify lifter rotation while assembling?
I will normally spec lobes designed for the .875 Ford lifter unless it's a full race effort beceause they are not quite as fast, but close. Which means they have similar area under the curve but are more forgiving both in terms of alignment and required spring pressure. I also verify all the lifters rotate easilly and many times this means swapping between bores until they all turn.
I would not be worried about using another flat tappet. I would be concerned about using another Hughes in that block especially if it's a large model.[/QUOTE
I spend extra time on the lifter bores making sure they were not sticking and rotated. The cam was 250 dur and 600 lift with 1.6 rockers.
