The current intake on John's motor is great for torque, but is known to sign-off around 5400-5500 rpm... even on a 502 motor. John has a 598. His rev limiter is currently set at 5600, and starts pulling timing out at 5400. You can feel the boat slowing in acceleration around 5400 with his current setup.
Along with the better flowing intake, he is also raising his rev limiter to 6200, in order to spin the motor to 5800-5900 without banging into the timing reduction.
I am pretty sure that both of these changes together, are going to make a noticable increase in power.
I do agree though... A visit to Mr. Whipple's Magic Kingdom, would make this motor really smile.
It's just a matter of time and money!
Chris