I would have thought with your vast SBM knowledge that you’d know the applications that use exhaust rotators also use shorter springs with them.
If you don’t think the info I posted about the valve lengths is accurate........ look it up yourself.
The main reason you wouldn’t normally use the HD valves in a HP application is because even when you eliminate the rotator, the stock retainer will have less installed height than if a std 4 groove valve is used...... as seen with the tip height disparity in the OP’s pic.
The .011” OAL difference is negligible.
