Hi Wuzak,
In reality, the Allison 1710 V-12 was designed from the outset for 4,000 rpm. The tractor-pull guys are running them at 4,500 rpm with no ill effects, with both 6 and 2-counterweight crankshafts.
The limiting factor in aircraft is the propeller, which cannot handle 4,000+ rpm reliably. It can take an occasional overspeed, but sustained 4,000 rpm operation would result in a broken propeller balde pretty quickly. At minumum the baldes would be stretched beyond operational limits, and would have to be replaced.