im thinkin bout porting/polishing my heads soon but wanna no wat kind of gains ill get from it ill hav them ported out a good amount and put 1.6 rockers back on and put the lt4 intake manifold on(which i already own so dont say i should just port the stock) along wit the holley 58mm TB that i hav wat kind of HP gains do u think ill get?

 

Depends on how good your porting is. If not done properly you can actually loose power. The LT4 intake is made to mate with the taller ports on the Lt4 heads and won't work too well with the Lt1 heads.

 

the intakes the one ment for the lt1 part # is 350-7107
and how could i end up losing power?

 

Because you can (and probably will) lose velocity (the speed at which the air moves though the ports). The trick is to know where/how to remove material that will allow and increase in flow without much of a drop in velocity. This take a very experianced hand. Not only that but if you grind on the wrong area you can go through the runnner and into the water jacket, thus ruining the head. Put it this way, I do 99% of the work on my cars, including engine assembly and chassis work (ie cages and such) and I would not in a million years want to port my own heads. To do it right ou need a flow bench to measure the flow changes at various lifts and you need to be able to get each runner the same or at least very very close.

 

Get your heads ported/polished by a professional or buy a new set of heads. That being said, there are varying degrees of power you can get out of a set of heads, and that all depends on how much money you're willing to put into it. Simply putting a better flowing head on the car isn't going to get you a bunch of power, no matter how well the heads flow because you're going to start to have too much flow for your stock cam. Your best plan is to go with a cam that is matched to your heads to you can optimize both, and then get a dyno tune.