I think 1.88 / 1.6 is about as large a valve as I'd recommend putting in these castings. The cross section in these things just isn't going to allow larger valves to work to their potential anyway IMO. Thats why I used a valve and seat profile that favor low / mid lift numbers, because I was pretty sure there was no hope for big numbers at high lift.
Same problem as the slanty head, there's enough "room" for much better & bigger valves, but casting inconsistencies make it impossible to do an entire head w/o taking a quick trip to watertown.
1.88's work great in a 3.50" bore, but doing a proper bowl deep enough to work at higher lifts is too risky. I cut some up and the "close" spots at the guide spot-face and short-side on some were scary before even starting the grinder!
