Odd that it sometimes won't run over 4,300, but other times will go to 5,000. Does it hold 5,000? I guess you must have some intermittent ignition issue or something.
The GM 292 dyno chart actually ended at 4,200; the 250 chart went up to 4,400 (gross HP peaks were 4,000 and 4,200, respectively). I don't think there's any doubt one will wind up to there, I just meant that the internet seems to enjoy clips of people trying to drop valves or put rods through blocks.
I think it might have also been a coincidence earlier with mine seeming to float something @ 4,700; I wound it to 4,800 today checking something and didn't notice it. I really probably should quit acting like a tree fell on my head, though...
Non-OT content: I wound it to 4,800 while checking how it sounded after finally cobbling a turnout onto the exhaust from some scrap laying around. No more deafening drone! Much better...