i just have a 305 w/ stahl and shift kit. hooker cat back exhuast(still has manifolds on it) k&n airfilters, smog assembly gone w/ holes welded shut on manifolds.just various little things done. I was wondering if i port my heads is this going to cause me to have to port the plenum and get a bigger intake, or can i just port the heads , bolt em on and have some more hp?

 

It's my understanding from looking at flows of the TPI that in stock form it flows about 200cfm. Your heads in stock form I believe do not flow that much; therefore, if you port your stock heads correctly you should realize some power gains. Most people also seem to get gains also from intake/runner/plenum mods before touching the heads....

Do both...since you have to take intake/plenum off to get to heads anyway.