i'm building a 455 pontiac. i have some 6X heads and i want to clean them up some. i know i need to trim the valve guide up some and round the short side radius some but could you tell me more exactly what to do and how much to take off? heres a pic of the intake port, on the short radius how much should i take off? should i just take enough off to round it off?

 

my second question is should i take any off inside of the bowl area just below the valve seat? it looks pretty small. i read in the standard abrasives thing that it sould be about 85% of the valve seat, it looks like mine is more like 75% or less.

 

on the valve guide how much should i take it down?

 

on the exhaust should i remove that lip on the short radius and open it up a little all the way around?

 

The short answer is YES and AS MUCH AS YOU DARE.
You cannot get this head too big for a 455. Go with the biggest valves that will fit too. Get the garden hose and squirt the water stream in to the ports. You'll get a good visualization of the high flow paths. Airflow does not like sharp edges or abrupt changes in direction.