It's hard to tell exactly, but looking at his photo below (from the thread I linked to above), the top of the locks do look to be protruding a bit more than usual from the 3100 retainers. If that is the case, the ID of the 3100 retainer may be
smaller and this will reduce the I/H of the spring- but I don't know what the 3100 retainer design will give for an I/H when used on the Vortec head, w/11/32" locks. For all I know, the 3100 retainer and the 11/32" locks might have a combined I/H of 1.8" or more- I can't tell from Spin's posts what's up w/that.
- in ANY event I would have serious reservations using a set-up that didn't provide full engagement
of the locks into the retainer's ID. I'd like to have a 3100 retainer and locks to measure. Just by looking at the 3100 locks should show easily if they're the same or thicker than the 11/32" locks- which they'd have to be (thicker that is) to work on a 8mm stem, yet have the same OD as a 11/32" lock.
It looks like what may be needed here, is a lock designed for the 3100 retainer's ID and the 11/32" valve stem's OD- unless that would make the locks too thin to be stable.