Zippy,
That are machined from 4340 prehard steel. This material typically measures between 30 and 35 Rockwell C (HRC). I measured a set of original small black Chevy retainers and they measured at between 31 and 32.
Just as a curiosity, the original LS lifter trays are made of nylon. It’s not about strength, it’s about wear resistance.
Thanks,
Stuart “Stan” Landreth.
|