Recenlty rebuilt 540/250 combos. New hydraulic rollers/top ends from Bob. Problem - Both engines start idle great and run perfect until around 2500 RPM's. At that point the port engine starts requiring more stick to keep up with the starboard. At 3K the port starts building boost and the boost guage is moving in unison with the throttle. At this point the sticks have about a 1.5" spread and the engine is really not making power. SB engine runs great well past 3K... Running TB IV - V6-14's with the initial set at 20*. Single 1050's. Engines have about five hours on them. I have pulled the heads thinking stuck valve, and checked the intakes for trueness. Thoughts?

You need to have a little more information; do some more troubleshooting first.

I have to ask; did you dyno engines?
Make sure the throttles are moving in sync.
Insure timing advance is equal at specific rpms.

This is a basic start.

Mark

Swap the carbs and see if problem follows .Then try swapping the blowers.
Do the blowers have the same hrs ?

check to see where timing is at various RPM'S 2000, 2500, 3000 ETC..See if they are the same ? personally don't like the merc dist...but thats just me...

What's the fuel pressure doing

I would swap the SC's and carbs. It sounds like you're not making boost.

Did it run good since rebuilding it 5 hours ago and just start doing this now or did it do it since you fired it?

Sounds like he's saying it does make boost but just doesn't have any power (port motor)?

+1...would have been a lot less work than pulling the heads!

I would verify timing and fuel before tearing things apart!!!!