[brian400ex]

I have a 355 sbc. mildly built. runs real strong. right now i have 305 heads that have been modified with 2.02 valves and ported. I have a chance at some World heads 1-037 sportsman heads. Just wondering if it would be an upgrade over the modified 305 heads. This is a street car.

[techinspector1]

I'm not sure anyone can answer your question intelligently. We have no idea to what extent the 305 heads have been modified, who did them, and/or if he knew what he was doing in the first place.

[F-BIRD'88]

If you were to port the Sportsman II heads correctly they will surely outperform the ported 305 heads.

As said it depends on how good a job was done on the 305 heads. I stay away from 2.02 valves for these heads but get real good results with full effort home porting and 1.94x 1.60 valves.
(porting 1" in is not near enough) They need the full boogie.
When done right, mid 230cfm flow is typical, with very good velocity and low/mid lift flow numbers too.

The out of the box as cast Sportsman II heads flow varies a lot depending on how the valve job was done. varies from 224cfm ( cheap valve job) to around 240cfm intake with a good valve job. (ya there is that much difference)

Of course when you port then and streamline that big *** fat valve guide boss the flow comes up a lot.

Both heads work very well when properly done.

The sportman II heads were intended to be ported to reap the best power potential on a high rpm race motor. The are capable of over 300cfm in fully worked form but such a head wants rpm, big cam etc.

If the cam is small , your typical rpm range while driving is not that high and the 305 heads were done well you won't see much difference.