I just had my heads worked on on my 69 351w and i got down to the pistons, and it looks like they have been hitting the valves, but when i bought the car the guy had put a comp cam rough idle cam in it with .500 lift on it, could replacing the old worn out stock springs with the springs rated for the cam fix this problem?

 

I dont think that new springs will solve the issue. I know that springs do have an impact as to how much the valve can move and can limit and bind the valve.
however, if the valves have been hitting the pistons then you most likely have some damage, like a bent valve stem or a valve that is not sealing.

you really shouls go with a new cam with a little less lift or redo you bottom end with pistons the clear or have reliefs in them.

when your heads were worked did you have them do a valve job?

 

Valve springs help the valve to follow the lift of the cam and rocker, especially at high rpm. Having the appropriate valve spring basically limits the affects of valve float. To some extent it limits the amount of travel the springs move because it provides resistance to opening. Unless you have very very very tight valve to piston clearance and you are turning high rpm and your valve springs are less stiff than the cam requires, I doubt new valve springs will help you if you are having piston to valve interference. In addition, if the valves in fact are hitting the piston, they do not do that long before they break, so it is a very serious issue if in fact that is what happened.

Questions:
1. What love lift is your cam?
2. What ratio rocker arms are you running?
3. What type if lifter are you using?
4. What rpm are you spinning the motor to?
5. What size valves and heads do you have?
6. Have you done a valve to piston clearance test?
7. Do you have pictures showing this damage?

 

That being said, put the right springs on. Do not install the old worn out springs.