How much Power can be made with a stock head by just upgrading the valve springs? No porting work or valve job.

 

springs don't add power...porting the head, bigger valves etc...are where the gains come from and while you're there install some bigger cams.

the stock head is still quite good, I know Al at dynoflash ran a stock head at the last shootout and trapped 150's

 

Springs, retianers, just allow you to rev higher without valve float right? This is why it's suggested that you upgrade with certain cams.