I have a 1986 corvette with a stock motor in it. I have the heads off and was wondering what i have to do to get a bigger cam in it. i think i would have to change the valve springs because i dont think they have enough lift to go much higher. I was also wondering how much porting and polishing them would help. And how big should i go on a cam  

In my opinion it is not worth porting a set of factory heads anymore as there are so many choices in the aftermarket that you can literally buy the correct cylinder head for your application,a great factory head for little money is a set of Vortec's,good flow,all new for around $300 ea.,you will have to change rockers and intake also but factory type rockers are not that expensive and a better flowing intake will help hp. that much more.
 As far as a camshaft,a good street cam would be around 215-220@.050 duration and .450-475" lift,but you will need to check with cam manufacturer on spring recommendation for the shaft you choose.  

First, on your heads. You've got the L98 heads, which are the same as the ones used on the current ZZ4 crate engine. (Are yours aluminum or cast iron?) While good aftermarket aluminum heads are cheap, they may not be cheap enough for your budget. The L98 heads are good heads, see what a machine shop would get to do some basic porting work and a three-angle valve job. Compare that to newer heads and make the call on what you want to spend.

Yes, those springs will have to be changed, the factory springs don't have enough muscle for any sort of performance. A mild cam with .450" - .500" lift will need a decent spring. I'd suggest the Crane 96802, or Comp equivalent 941 will work for either a flat tappet or roller cam. If you convert your motor to a hydraulic roller, set the springs up with about 120 lbs. on the seat. For a flat tappet, 105-110.