if i were porting a set of heads to get some decent gains, i would match the port with the gasket (stock type gaskets will generally always leave you some porting room) slowly and work my way in keeping the flow as smooth as possible. it's ok if the port gradually gets smaller because this should help the air gain velocity as it goes in. if you have a means to safely remove valve springs, i would highly consider taking the valves out and working on the area above the valve seats because it will probably have a sharp "cliff" kinda structure that inhibits direct airflow down into the combustion chamber. in order to get a more complete burn of air and fuel, do what jthorn suggested on the combustion chambers by smoothing up the metal and possible egr bumps. this will technically lower compression ratio, so it may not provide a ton of power in itself if any. remember that taking off too much metal can't be fixed nearly as easy as not taking off enough metal. if you're dealing with aluminum, it's going to be pretty easy to cut through. for the intakes, i'd port match them and use flap wheels to smooth out the flow of the runners. like with the heads, i'd gradually remove metal as you go into the runners, but it's not necessary to hog it out as big as you can unless you've got something that can support the flow capability. if you go too big on the intake you may lose low end air velocity which is going to move the torque higher into the powerband. it's kinda hard to go "too big" on the heads as they are a large restriction on the sixers.

 

ok thanks, when you say port match do you mean port the intakes to match the gaskets? and what is flap wheels? thanks

 

you use the gaskets as a guide so you can port both the heads and intake to be the same size. flap wheels look like this and are good for making sure runners and ports are even and smooth. if you haven't seen this site before, it should help explain a lot of things. http://www.sa-motorsports.com/diyport.shtm