How are you guys peening the tube in the lifter bores? I've seen and heard of guys breaking the lifter bore boss out by using hard, non-annealed copper tubing and trying to drive the peen tool down through the lifter bore.

The reamers that have had the nose machined to the original bore size seemed to work OK if the "pilot" was sufficiently long, but the block had been put in a machine of some type to control the feed and keep everything stable.

The straight reamers run with a hand drill look like they want to deflect towards the oil galley once the reamer hits that open spot. I've always elected to bite the bullet and have the lifter bores bushed.